key: cord-0036408-j8rgke5u
authors: Spieler, Peter; Rössle, Matthias
title: Respiratory Tract and Mediastinum
date: 2012
journal: Nongynecologic Cytopathology
DOI: 10.1007/978-3-642-24719-4_2
sha: 68f6bf2c0d6f010b60c749e1ccc5e655cc79b1d3
doc_id: 36408
cord_uid: j8rgke5u

Normal cytology, abnormal and atypical cells, non-cellular components, and infectious cell changes are largely described together with benign, malignant, and neuroendocrine lesions regarding exfoliative and aspiration cytology of the lung. A separate section broadly addresses diagnostic findings and differential diagnoses in bronchoalveolar washings. The section ‘Fine needle aspiration biopsy of mediastinal disorders’ covers in particular biopsy techniques, accuracy of liquid-based cytology, and the complex lesions of the thymus gland. Cytodiagnostic algorithms of the major benign and malignant pulmonary and mediastinal lesions and their respective differential diagnoses are additionally presented in synoptic setups.

The bronchial brush direct smear preparation. The mucusrich material adherent to a brush is smeared by rolling the brush over one or more glass slides followed by immediate fixation. This method should only be used by skilled bronchoscopists or an attendant cytotechnologist. Cytocentrifugation is particularly applied to process lavage fluids. Liquid-based cytology is increasingly used for the processing of FNAB material [103] . The advantages and interpretative cautions concerning the liquid-based preparation are reported in the literature [75] and in various chapters of this work (e.g., Sect. 10.1.2.2, p. 634).

The Papanicolaou (Pap) method is the most widely accepted staining method for cytologic preparations of respiratory specimens.

The accuracy of the different modalities as to cancer diagnosis has recently been summarized from published data by Schreiber and McCrory [84] .

Sputum has been the most frequently examined sample from the respiratory tract for many decades. Since the intro-duction of fiberoptic bronchoscopy and the wide use of FNAB, sputum cytology has diminished [58] . Pulmonologists and institutions specialized in lung diseases prefer primary investigation using invasive and more directed methods based upon imaging results and supported by auxiliary device.

Sputum specimens are prepared as described. In patients who cannot produce sputum by deep coughing, a sputum sample may be induced by inhalation of an aerosolized solution [72, 80] . The vapor stimulates mucus production and may enhance the coughing stimulus. Another useful physical technique for provoked expectoration is the external percussion and vibration of the chest wall [96] . Postbronchoscopy sputum is an approach used to increase diagnostic accuracy. However, from our experience, a high percentage of postbronchoscopy samples are extremely sanguineous and difficult to evaluate.

Deep-cough specimens and their immediate transfer to the cytology laboratory after collecting are of utmost importance for reliable diagnostic results .

The development of the flexible fiberoptic bronchoscope has enabled the operator to reach much smaller bronchi compared to those formerly attained by the rigid bronchoscope.

Specimens are obtained from the periphery of the bronchial tree by: − Aspiration of localized secretions. − Instilling a few milliliters of a saline solution through the bronchoscope and re-aspiration of the fluid together with the exfoliated cells. − Brushing a conspicuous lesion with a brush inserted through the endoscope.

Laboratory procedures and technical aspects concerning bronchoalveolar lavage (BAL) are discussed in Sect. 2.3.2, p. 176. Aspirates and washings, and brush samples rinsed in an appropriate solution (balanced salt solution or cell medium) are to be centrifuged. Subsequently, smears are prepared from the cell button. The different preparation techniques including bronchial brush direct smear preparation have been described above.

Presence of blood in aspirates and brushings is frequent and found most particularly in patients with primary lung cancer involving the bronchial system. Vigorous brushing may provide large tissue fragments from the bronchial wall composed of connective tissue and smooth muscle bundles ( Fig. 2.1 ). z z Endoscopic ultrasound-guided FNAB (EUS-FNAB): In these days, fiberendoscopes can be equipped with highly sophisticated, tiny ultrasound transducers attached to the tip of the instrument. Transbronchial and transtracheal endoscopic ultrasound allows the operator to visualize intramural/submucosal lesions and lesions in adjacent mediastinal compartments that are not detected and not accessible by other techniques, due to their location or their size [78] . Most of these lesions can reliably be evaluated by EUS-FNAB. The same technique is applied for transesophageal ultrasound-based minimally invasive morphologic investigation of disorders located adjacent to the esophagus, in the dorsal mediastinal space, and in dorsal regions and the upper lobes of the lung [22, 99, 109] . Transbronchial, transtracheal and transesophageal EUS-FNAB has become an important tool for staging lung cancer at the time of diagnosis and for assessing diagnosis on otherwise undiagnosed pulmonary and mediastinal masses. [2, 35, 47, 54, 65, 101] . With this procedure, numerous invasive surgical interventions (mediastinoscopy, thoracotomy, thoracoscopy) can be avoided [115] .

Major portions of the upper and lower respiratory tract are lined by a pseudostratified cuboidal and columnar ciliated epithelium. The function of these cells is the proximal transport of the mucus stream. For this reason, each cell carries approximately 300 cilia (average length 6 µm) anchored in an apical terminal plate.

Clara cells are nonmucous and nonciliated secretory, domeshaped cells found in the bronchioles of the lungs (bronchioles represent the transition from the conducting portion to the respiratory portion of the lung system) and account for the majority of nonciliated bronchiolar cells. They protect the bronchiolar epithelium secreting mucoid and nonmucinous products and contribute to surfactant production. They can also multiply and differentiate into ciliated cells. (Fig. 2. 3)

Ciliocytophthoria is a specific form of degeneration of ciliated columnar epithelium of the respiratory tract. It was first described by Papanicolaou in 1956 [71] . The cellular alteration has been regarded as a common finding in viral infection.

z { Cellular changes include detached ciliary tufts (remnants of ciliated epithelium) and degenerating cytoplasmic fragments with a pyknotic nucleus. Additional round eosinophilic cytoplasmic inclusions may be present. Look-alikes may be seen in body fluids, especially of peritoneal origin and in washings of the pouch of Douglas. They can cause confusion with ciliated protozoa.

Densely clustered basal cells with their deeply stained nuclei may simulate small-cell carcinoma . This is particularly true for bronchial specimens where the cells are entrapped in thick blood masses . However, small cellular and nuclear size together with orderly arrangement are not compatible with any malignant neoplasia .

( Fig. 2. 2) Alveolar macrophages (AM) are derived from precursor cells called monocytes that first develop in the bone marrow [100] . Monocytes travel throughout the body in the circulatory system of blood. When needed, circulatory monocytes move into tissue, where they become macrophages. Another mechanism of accumulation of alveolar macrophages is hypothesized by increased local proliferation [90] . Alveolar macrophages serve as the front line of cellular defense against respiratory pathogens, clearing the air spaces of infectious, toxic, or allergic particles and ingesting carbon and other inhaled substances [88] . An alveolar macrophage is a mononuclear cell with a high phagocytic capacity on the epithelial surface of lung alveoli. The presence of this cell type in sputum indicates adequacy of the specimen submitted for microscopic evaluation. Phagocytized material in the cytoplasm of AMs: The most common material is carbon. In cases of lipid pneumonia, however, AMs exhibit large sharply outlined vacuoles containing fat [50] . The startling cell size and cytoplasmic structure of fat-laden macrophages may overlap with cytologic features of clear cell adenocarcinoma or liposarcoma. However, the AM nuclei are bland and mucus cannot be identified either. Immunocytochemical studies can confirm the cell type in cases with ambiguous cytomorphology (CD68 positivity versus negativity for cytokeratins and other epithelial markers). Phagocytosis of hemosiderin is a sign of previous blood discharge into the alveolar space. Hemosiderin pigments appear as large roundish or square aggregates that are refractile and greenish or rusty colored. For greater detail on hemosiderin pigment, see Sect. 2.3.4.8, "Alveolar Hemorrhage Syndrome," p. 184.

Other noncellular elements are discussed in Sect. 2.1.5, p. 115

Sarcoidosis. Langhans-type giant cells together with densely crowded activated epithelioid cells and benign small lymphocytes are highly suggestive of sarcoidosis. Activated epithelioid cells are characterized by enlargement and a more spherical configuration, nucleoli are obvious. Necrosis is absent with few exceptions. More information on sarcoidosis is provided in the Sects. 2.3.4.1, p. 179 and 15.2.5.6, p. 933. Characteristic cellular components of sarcoidosis are rarely encountered in respiratory exfoliative samples. Yet induced sputum, as a noninvasive technique, may be of diagnostic help in pulmonary sarcoidosis regarding the lymphocyte counts [19, 66] . In contrast, EUS-FNAB has been shown to be an extremely accurate method for diagnosing sarcoidosis in patients affected by mediastinal disease [55, 111] . Mycobacterial granulomatosis is discussed in Sect. 2.1.6.1, p. 116.

Neutrophils are omnipresent in exfoliative cytologic specimens from the bronchial tree. Abundant polymorphonuclear leukocytes suggest infectious disease. Organisms may be recognized in conventionally stained cytologic specimens, but they are detected with higher accuracy using special stains such as Gram, Ziehl-Neelsen, periodic acid-Schiff reaction (PAS), and silver stains.

These cells are associated with chronic inflammatory processes, granulomatous disease, or acute viral infections. Numerous lymphocytes in a circumscribed area in a smear preparation of sputum and other bronchial material most likely originate from a ruptured lymphoid infiltrate/lymph node located in the bronchial mucosa. Transformed lymphoid cells and starry-sky cells may occasionally be encountered, which makes it easy to exclude small-cell malignant lymphoma (chronic lymphocytic leukemia) and small-cell carcinoma.

z { Benign lymphocytes are smaller than cells from a lymphoid or epithelial neoplasia. Nuclear texture of benign lymphocytes is bland, and nucleoli are rare and inconspicuous.

Numerous environmental irritants, various microbiological agents, drugs, chronic lung disorders, embolism [9] , bronchial tumors, destructive granulomatous lesions, injuries due to instrumentation, and infarction [41] may induce hyperplastic processes including reactive (atypical) cell changes in the epithelium of the respiratory tract [40] .

Squamous cells that exhibit atypical or frankly malignant features may originate from a regenerative, dysplastic, or neoplastic lesion in the oral/pharyngeal/laryngeal area . In general, only a small number of such cells will be present in exfoliative respiratory specimens [52] .

Squamous metaplasia in reference to the tracheobronchial system means replacement of the ciliated epithelium with a stratified epithelium that resembles immature squamous epithelium. Squamous metaplasia occurs as an abnormal repair response to irritations and to a multitude of environmental toxic agents and organisms [98] . Cigarette smoking is one of the most frequently cited causes responsible for the development of squamous metaplasia [4] .

z { Metaplastic squamous cells may appear discrete, but typically in small and larger cell groups. The monomorphic cells are arranged in monolayered sheets, whereas the polygonal cell shape gives the sheets a cobblestone-like appearance. 

(Figs. 2.8 and 2.9) Metaplastic squames may undergo changes that should classify them as atypical cells.

z { The cells show an increased N/C ratio. The nuclei are slightly irregular in outline and exhibit granular chromatin, hyperchromasia, and nucleoli. These cellular changes can be associated with prolonged nonneoplastic abnormal conditions of the bronchi and lung, or with carcinoma. It is virtually impossible to differentiate between different grades of atypia and to exclude premalignant epithelial lesions (dysplasia) by light microscopy [12] ( Fig. 2.31 ).

Abnormal squamous cells may exfoliate from the oral mucosa. Various diseases such as inflammation, ulceration, infection, chronic mucosal irritation, and others may be responsible for atypical squames, particularly in sputum probes. Cytologic features of the most common disorders of the oral mucosa and adjuvant diagnostic procedures that z Image cytometric DNA ploidy assessment can distinguish between reactive atypia and atypical squamous cells with preneoplastic potential . The latter provide DNA aneuploidy, which requires further investigations; a diploid DNA histogram indicates reactive atypia, which should result in monitoring the patient by repeated cytology over a long period . z z Both the progression rate and the regression rate of dysplastic lesions of various morphologic grades should not be disregarded [12] . Both severe cytologic atypia and DNA aneuploidy do not necessarily imply progression to invasive growth .

Reactive forms of bronchial epithelial cells cover a wide spectrum ranging from mild cellular changes with inconspicuous nuclear atypias and attached cilia to marked cellular/ nuclear alterations that simulate adenocarcinoma [27, 49, 60] .

This is a common alteration, most frequently encountered following instrumentation. The cellular shape, terminal plate, and cilia are well preserved, whereas cellular size varies depending on the number of nuclei. The N/C ratio and nuclear features are bland.

Mild Reactive Cell Changes (Fig. 2.10A ). Mild irritation of the bronchial epithelium may occur in a number of chronic lung diseases including bronchial asthma, chronic bronchitis, bronchiectasis [43, 64, 82] and tuberculosis. In the majority of cases, the exfoliated single cells and hyperplastic mucosa fragments with mild atypias are accurately recognized as benign, if the cytologic features as indicated below are taken into consideration. Severe atypias due to irritation and proliferation of the bronchial epithelium are easily mistaken for adenocarcinoma. Based on our experience, such changes are mainly caused by viral infections, pulmonary infarction, chronic lung disease with recurrent infections (e.g., bronchiectasis), instrumentation, and toxic chemical agents (e.g., oxygen inhalation) [17, 42] . They may also be observed after radiation therapy [108] and chemotherapy [15, 97] .

Guzman and coworkers showed that proliferative type II pneumocytes share many antigens with epithelial tumor cells, including keratins and TTF-1. Thus, immunocytochemical tests are of little help to differentiate between reactive pneumocytes and malignant cells [33] . DNA Ploidy Several reports suggest DNA analysis on cytologic respiratory samples to be a reliable tool for the detection of early lung cancer and of high-risk patients with cellular atypias [5, 70, 95, 112] . Automated DNA quantitation by image cytometry on cells in sputum and bronchial washings appears to be a sensitive method for the detection of malignancy and therefore also seems suited for screening procedures [44, 51] ; DNA aneuploidy serves as a marker for malignancy [113] . DNA flow cytometry has also been applied to various respiratory cytology specimens as an adjunct in cancer diagnosis; diagnostic accuracy is expected to increase [116] .

As stated earlier, carcinoma cells are difficult to separate from benign epithelial cells showing marked ionizing radiation-induced degenerative changes . Since radiotherapy can cause major quantitative and structural alterations to the nuclear chromatin, DNA quantification will also be of little help in this setting and may contribute to enhanced confusion in assessing malignancy .

Cytomorphometric Analysis A few reports discuss the significance of morphometric criteria distinguishing between benign reactive epithelial proliferations and bronchioloalveolar carcinoma [24, 117] . Molecular Genetics Recent studies indicate that different genetic analyses using PCR and fluorescence in situ hybridization (FISH) assay yield valuable results for the detection of precancerous lesions and early-stage cancer [36, 45, 48, 89] . On that score, we recently contributed to a bi-institutional study that showed that a commercially available multitarget FISH assay (LA Vysion; Abbott/Vysis; Downers Grove, IL, USA) simultaneously analyzing chromosome 6 and the 5p15, 7p12 (EGFR gene), and 8q24 (MYC gene) loci, is very helpful in elucidating equivocal lung cytology, differentiating between regenerative-benign and neoplastic cell changes [83] .

Numerous noncellular structures may be present in cytologic samples from the respiratory tract. Some of them may indicate a specific pulmonary disorder, some are derived from the patient, some may have been inhaled, and some are contaminants from the environment to the cytologic specimen. Some of these elements may be confusing and may lead the less experienced cytologist to incorrect diagnoses.

Curschmann spirals are casts of mucus showing varying degrees of inspissation. They are frequently associated with bronchial asthma and heavy smoking, but the common cause is bronchial obstruction [102] .

Mucus spheres with a pseudo-organoid appearance or with deep staining should not be misinterpreted as cells or nuclei.

Alveolar proteinosis may deliver amorphous masses into bronchial canaliculi. Charcot-Leyden crystals may be found together with eosinophils in people who suffer from any form of allergic disease; however, in respiratory material they constitute a distinct sign of bronchial asthma. The crystals are derived from disintegrated eosinophils. Charcot-Leyden crystals vary in size and reach a length up to 50 µm. They are composed of two slender pyramids joining at their bases and tapering into pointed ends, they stain purplish-red with the Papanicolaou method ( Fig. 2.14) .

Corpora amylacea are rounded, hyaline bodies presenting with striations and concentric rings; they are condensates of glycoproteins. Corpora amylacea are formed in the bronchial tubes and in the alveolar spaces. Association with chronic lung disorders is well known.

Calcospherites (synonym: psammoma body) appear like corpora amylacea but they contain various anorganic compounds and are calcified. Calcospherites are related to lithiasis of the lung and to primary and secondary adenomatous cancers.

Ferruginous bodies (Figs. 2.15 and 2.75) result from inhalation of diverse mineral fibers that become coated with varying substances; ferroprotein is the fraction that yields the typical golden-brown color in Papanicolaou-stained specimens and the positive reaction with iron stains (e.g., Prussian Blue). A high percentage of ferruginous bodies are seen together with one or more stimulated macrophages, which interact in the forming of these structures and try to ingest the foreign particles [20] . The encrustation of the fibers is extremely irregular, giving them the characteristic beaded bamboo shape segmentation of the shaft and blebs and buds on the branching and bulbous protrusions at both ends. Beaded slender rods with a smooth surface of the protrusions at both ends are most likely associated with asbestos bodies. Asbestos fibers, in interaction with other toxic elements, are responsible for asbestosis (and pulmonary fibrosis) of the lung, lung cancer, and mesothelioma. See also Sect. 2.3.4.9, "Pneumoconioses,." p. 184. 

The cytomorphologic recognition of certain viral infections with their specific cellular alterations has a practical significance not only in samples derived from the respiratory tract, but also from many other organs of the human the body, e.g., in cervical smears, cerebrospinal fluid, and esophageal and skin brushes. [29, 61] 

Mycotic infections have significantly increased: − Since the implementation of chemotherapeutic and immunosuppressive drugs in therapeutic regimes. − Because of the obvious increase in malignancies and longer patient survival. − Because of higher incidence of immunocompromising viral infections.

− The majority of mycotic organisms can be identified in cytologic preparations from the respiratory tract. Routine cytological stains are usually adequate for identification. Special staining procedures are helpful in samples containing only a few fungi and in samples with concomitant acute florid inflammatory infiltrates that obscure the organisms. Grocott-Gomori methenamine-silver stain is the best stain to use, but periodic acid-Schiff may also be effective. 

Opportunistic organisms are saprophytes that contribute to the normal flora in different body sites, but that may become pathogenic in immunosuppressed individuals. Sputum specimens, endoscopically sampled respiratory material, and fineneedle aspirates exhibiting fungi of any opportunistic type together with a purulent inflammation should raise suspicion of a mycosis. z { Hallmarks: The organisms are tiny and more or less spherical, measuring 4-5 µm in diameter. The capsule is smooth and deeply stained. Disintegrated cysts show a single deep groove or may be crescent shaped or crinkled. Focal thickening of the cyst wall is easily recognized by light microscopy. This phenomenon has been reported as an important diagnostic criterion for the identification of Pneumocystis and to differentiate them from yeast-form fungi [107] . Organisms presenting as a dense, foamy mass with irregular margins on Pap-stained smears is characteristic in such a manner that an accurate diagnosis even without special stains can be rendered [30, 85] . z { Small numbers of organisms that are haphazardly arranged can only be recognized by use of special stain (methenamine silver). The diagnostically reliable dense foamy masses of organisms generally occur in bronchoalveolar lavage and in lavage and brushing from the very peripheral areas of the bronchial system, as well as in fine-needle aspirations. Induced or postbronchoscopy sputum specimens may have an acceptable diagnostic accuracy as well [10] . Spontaneous sputum has a low sensitivity in detecting Pneumocystes; therefore this method should not be applied in the routine evaluation of patients with AIDS and pulmonary complaints [18] .

Pneumocystes should not be confused with non-living elements such as degenerating and leached out erythrocytes clustering together. Furthermore, it is difficult to separate Pneumocystis from other organisms, in particular from yeast-form fungi such as Candida species and Histoplasma [13, 107] .

A number of parasites can be detected cytologically in respiratory material and have been reported in the medical literature including Strongyloides stercoralis [46, 114] , Echinococcus (pulmonary echinococcosis) [68] (Figs. 9.7, 9.8, 12.5) , Trichomonas [21, 67] , Microfilaria [38, 57] , Toxoplasma gondii, Cryptosporidia [92, 93] , and others. Low magnification reveals connective tissue and smooth muscle bundles (arrows) in bronchial brush cytology (from the right lower pulmonary lobe) (Pap stain).

The specimen is stained according to Papanicolaou (high magnification). Individual ciliated bronchial epithelial cells. Goblet cells (arrow), nuclei are displaced to the periphery of the cell, mucoid inclusions appear foamy and stain pinkish. Carbon-laden (anthracotic pigment) macrophages (upper right), nuclei show features indicating reactive changes (rounded shape, prominent nucleolus). Degenerating epithelial cells (arrowhead). 

A compact cluster of reserve cells. Note the small size of cells and nuclei in comparison to nuclei of the blurred columnar epithelial cells(bottom), the deep-blue-stained nuclei, occasional nuclear molding, and the small rims of homogeneous cyanophilic cytoplasm (bronchial aspirate, Pap stain, lower magnification).

Three Langhans-type giant cells presenting in varied positions (FNAB of lung, low magnification, Pap stain): (1) The multinuclear cell at the right side of the field gives an impression of three-dimensionality of the cell.

(2) Horseshoe-like arrangement of the nuclei is best recognized in profile (centrally located cell).

(3) The same nuclear arrangement is seen top-down (cell on left). Cytology is highly suspicious for mycobacterial granulomatosis. Ziehl-Neelsen staining for acid-fast bacteria was negative (no information as to further investigations).

Two aggregates of loosely arranged activated epithelioid cells are shown (arrows). Enlarged nuclei exhibiting loose reticular chromatin and usually distinct nucleoli. Interspersed small lymphocytes and absence of debris raise suspicion of sarcoidosis (no further diagnostic evaluation) (sputum probe, Pap stain, lower magnification).

A flat sheet composed of metaplastic squamous cells is depicted at high magnification. The polygonal shape of the cytoplasm and sharp cytoplasmic borders show a cobblestone-like aspect. Few cells exhibit keratinization. Note patternless or shadowy nuclei and occasional perinuclear cytoplasmic clearing (arrows) (sputum probe, Pap stain).

Two examples of atypical squamous metaplastic epithelium are presented. The cytologic specimens have been stained with the Papanicolaou method.

A sputum probe of a 55-year-old smoker suffering from COPD shows numerous sheets of abnormal squamous metaplastic epithelium. High magnification of loosely arranged cells discloses characteristics of squamous metaplasia (sharply delineated cyanophilic cytoplasm, partly intact cobblestone-like cell arrangement, perinuclear clearing). Still, variability in cell size, irregular chromatin texture, and distinct nucleolar pleomorphism indicate atypia. Follow-up: Clinical and cytologic long-term follow-up revealed no malignancy.

(case #2) FNAB of the lung in a 54-year-old woman reveals an inflammatory infiltrate and few highly atypical squamous cells (low N/C ratio, severe nuclear irregularity, hyaline cyanophilic and concentrically laminated cytoplasm, intercellular bridges marked by an arrow) (high magnification). Apparent degenerative nuclear changes (nuclear vacuoles, patternless clear nuclear areas, and absence of nucleoli) do not permit a conclusive diagnosis of malignancy. Tissue diagnosis: Open thoracotomy followed by microscopic evaluation of excised tissue rendered a diagnosis of an abscess accompanied by severe reactive change of the bronchial and alveolar lining cells. A patient with bronchial asthma underwent bronchoscopy. The bronchial aspirate contains crystalloid elements. Note typical shape, staining quality, and distinct variation in size of the Charcot-Leyden crystals (arrows). Background usually comprises degenerating eosinophils (Pap stain, high magnification).

Image-guided FNAB of a nodular lesion in a male patient's right lung. Squamous cell carcinoma was found in a subsequent sputum probe. Asbestos bodies of varied size (lower right) and a large pseudo-asbestos body (upper left) are seen. Both ferruginous body variants are partly engulfed by macrophages (Pap stain, high magnification). A sputum specimen showing morphologic characteristics of mycobacterial infection. A Lower magnification reveals key features of mycobacterial infection: three-dimensional aggregates of epithelioid cells partially exhibiting extremely slender and pyknotic nuclei (arrows), caseous detritus and tiny calcified deposits (Pap stain). Compare current epithelioid cells with those in a case of probable sarcoidosis (Fig. 2.6) . B Strong positive reaction of acid-fast bacilli with Ziehl-Neelsen staining (oil immersion, Pap-prestained smear, objective ×100).

Bronchial brushing containing numerous columnar bronchial epithelial cells, which occasionally show cilia. Abnormal cells exhibit virus-associated changes such as cellular enlargement, multinucleation, and pale nucleoplasm ; cell shape and N/C ratio are usually within normal range. (Pap stain, high magnification). Viral culture tests (undertaken from cytologic material) provided a positive result for poliovirus type 1.

Smears of a sputum sample present epithelial cells exhibiting characteristic herpes simplex features: nuclear ground-glass appearance, nuclear inclusions, marginalization of the chromatin (arrow), and a small to medium-sized cytoplasmic rim. The selected cell cluster may lead the inexperienced examiner to a false diagnosis of adenocarcinoma. (Pap stain, high magnification).

Key features of cellular alterations caused by RSV: syncytial clusters of epithelial cells showing virus-induced nuclear features (marginalization of the chromatin, ground-glass-like nucleoplasm), and few sharply outlined cytoplasmic halos (the commonly associated darkstained inclusions are not in focus) (bronchial aspirate, Pap stain high magnification). Single round to oval yeast cells of variable size, dyads of yeast cells, and pseudohyphae are shown against a background of acute inflammation (sputum sample, Pap stain, higher magnification).

Pulmonary aspergillosis that was detected in both exfoliative bronchial material and fine needle aspirate of the lung.

Many branching septate hyphae that are characterized by prominent cell walls and steady width are embedded in an acute inflammatory background (sputum probe, Pap stain lower magnification).

Post-therapeutic follow-up of the aspergillus pneumonia by means of FNAB of the lung and silver stain: small fungal fragments and degenerating hyphae are much more easily identified by methenamine silver staining than by conventional cytologic staining methods (high magnification). Differential diagnosis considerations are much the same as discussed for pulmonary hamartomas (see previous section). [73, 117] Granular cell tumor is a benign mesenchymal tumor assumed to be of Schwann cell origin. The tumors occur in many organs of the human body. Granular cell tumors of bronchial and tracheal [49] origin protrude into the bronchial/tracheal lumen and may mimic carcinoma. Thus, abundant granular cells can be found not only in FNABs but likewise in brushings and washings obtained during endoscopy. Granular cell tumor has a distinct microscopic appearance that should permit diagnosis in cytologic specimens. Immunocytochemistry and Cytochemistry (Figs. 1.63B and 1.63C) Tumor cells stain immunocytochemically positive for the S100 protein, neuron-specific enolase, and vimentin. The cytoplasmic granules are PAS-positive and diastaseresistant [57] .

Granular tumor cells may be misinterpreted as foamy alveolar macrophages, as cells from primary or metastatic lowgrade oxyphilic lesions, or as cells from malignant melanoma. [93] 

Lung metastasis from a primary germ-cell malignancy in an extrapulmonary location with previous successful therapy may mimic mature teratoma . 

A characteristic, but inconstant feature of clear cell tumors is the presence of abundant cytoplasmic glycogen reliably verified by a positive periodic-acid Schiff reaction [64] .

Most tumor cells demonstrate strong positivity for HMB-45 and Melan-A. Immunoreactivity with antibodies for CD34 points out the endothelial cells of blood vessels. Negative immunostaining has been established for epithelial antigens, keratins, factor VIII, smooth muscle actin, S100, and for RC-CMa (renal cell carcinoma-associated cell marker) [64, 91] . [28, 24] Oncocytomas in bronchial glands are usually small and occur extremely rarely. They are incidentally found in bronchial brushings and secretions after endoscopy. Amyloid tumor is a tumor-like accumulation of amorphous amyloid protein in the lung parenchyma. Pathogenesis of nodular pulmonary amyloidosis is not clearly understood. In contrast, diffuse amyloidosis is usually part of systemic amy-loid disease or caused by lymphoid neoplasms [65] . Lung deposits may occur alone or as multiple foci in both lungs [115] .

z { Congo-red stain positivity by light microscopy and apple-green birefringence upon polarization are reliable diagnostic criteria. Protein masses may be accompanied by a lymphoproliferative infiltrate and foreign body giant cells. (Fig. 16.19 ) z z The term "thoracic endometriosis" refers to the respiratory manifestations that result from the presence of endometrial tissue in thoracic structures. The pathogenesis of thoracic endometriosis is still unclear. Hematogenous and lymphatic embolization of endometrial tissue and other mechanisms have been discussed [9, 131] . In cases with pleuropulmonary nodules, FNAB may be used to establish a definitive diagnosis [39] .

z z The clinical manifestations consisting of pneumothorax, hemothorax, and hemoptysis classically recur in accordance with the menstrual cycle [9, 82] .

Characteristic cytomorphologic properties in FNAB specimens are also presented in several chapters of this book, for instance in Sect. 16 The tumor can occur at any age, but it is one of the most common lung tumors in children. The nature of this disorder (reactive versus neoplastic) has not been completely elucidated yet.

Histology shows a wide spectrum of fibroblastic/myofibroblastic proliferation and varying infiltrates of histiocytes, lymphoid cells, and mature plasma cells. There is a considerable overlap of multiple phenotypes of this lesion.

The cytologic pattern has repeatedly been described in the current literature: 

z z Inflammatory pseudotumor is usually diagnosed accurately by FNAB, but the cytologic findings are rather suggestive and nonspecific [45] . A tumor subtype with a lack of plasma cells and aggressive forms of the disorder comprising atypical mesenchymal cells may raise diagnostic difficulties with benign and malignant spindle cell lesions [47] 

General Comments z z Lung cancer is currently the most commonly diagnosed noncutaneous malignancy in the world and the most common cause for cancer mortality worldwide. Clinical, epidemiologic, and experimental evidence exists that cigarette smoke has strong carcinogenic effects. Thus, future smoking habits will greatly influence incidence and mortality of lung cancer and will also have an impact upon the histologic tumor types. Other factors that are contributing to the development of lung cancer include asbestos exposure, ionizing, and chemical agents of which environmental pollution supports a synergistic effect [87, 105] .

z z Although the World Health Organization (WHO) classification [119] , in contrast to the recently published IASLC/ ATS/ERS lung adenocarcinoma classification [119A] , does not address cytology, the authors prefer the WHO nomenclature for practical reasons as well as cytologic purposes. From cytology alone, it is possible to diagnose the major tumor categories and certain tumor subtypes of lung cancers, but it is definitely not possible to identify each tumor type within the WHO nomenclature [8] or the IASLC/ATS/ERS lung adenocarcinoma classification.

z z A definitive treatment of lung cancer is feasible, solely on the basis of cytological findings [14] .

z z Examination of one or repeated sputa will detect the more centrally located neoplasms, whereas washings, brushings, and FNAB will collect adequate samples from tumors in the periphery of the bronchial system and from subpleural lesions. Combined application of multiple sampling methods in the same session can considerably enhance the impact of cytology on primary lung cancer diagnosis and tumor staging.

z z The heterogeneity of lung cancers is less frequently detectable in cytologic specimens compared to histologic sections from multiple tumor areas. For cytologic diagnosis of adenosquamous carcinoma, respiratory material or fineneedle aspirates must exhibit malignant cells with evidence of both keratinization and mucus secretion. In our cytologic practice over three decades, we could only sporadically find a combination of small-cell/large-cell carcinoma.

Tumor heterogeneity versus synchronous primary tumors of different localization within the respiratory tract has to be considered using exfoliative cytologic methods [125] .

z z Due to possible therapeutic consequences, the diagnostic term "non-small-cell carcinoma" should be avoided also for cytologic specimens. Additional immunocytological and molecular genetic testing further differentiates adenocarcinoma and squamous cell carcinoma in most cases [119A, 119B, 106A] . Molecular diagnostic methods detecting tumor specific genes in lung cancer specimens for diagnostic and therapeutic purposes (e.g., EGFR or KRAS mutation, ALK-rearrangement) may also be performed on a cytological specimen [2, 119B] . Most particularly, mini-mally invasive FNAB should provide enough cellular material for such supplementary studies.

z z A preinvasive (in situ) lesion of squamous cell carcinoma was postulated by Black and Ackerman in 1953 [10] . The progression of dysplastic changes in squamous metaplastic epithelium to carcinoma in situ and invasive cancer has been documented in the past and is currently accepted [22, 103] . [60] . − Squamous cancer of the oropharyngeal region. In contrast, invasive squamous cell carcinoma of the common type includes larger cells with pronounced polymorphism, necrosis, and an inflammatory background.

General Comments z z Squamous cell carcinoma (SCC) is still the most frequent histologic type among lung cancers and highly attributed to cigarette smoking. This tumor type accounts for approximately 50% of lung cancers in males and 20% in females. Epidermoid carcinoma is known as a neoplasm of the major bronchi, but a large number of these tumors may start in a small peripheral bronchus followed by a usually centripetal extent into the larger bronchi [34] .

z z Histological variants of SCC include tumors with papillary, clear cell, small-cell, and basaloid features. In rare cases, such features are present throughout the whole tumor mass; more commonly they occur focally. z z SCCs are graded histologically in well-differentiated (extensive keratinization), moderately differentiated (keratinized tumor cells but not widespread), and poorly differentiated (focal signs of keratinization) tumors. Histological grading may reliably be used on highly cellular FNAB samples but to a lesser extent on exfoliative respiratory cytology. z { Absence of tumor necrosis and a sanguineous background is extremely rare in cytologic specimens that contain SCC cells, independent of the sampling method.

Differential diagnosis considerations include a variety of benign and malignant conditions. z z Squamous cell carcinomas composed of predominantly small rounded malignant squamous cells may more likely originate from the periphery of the bronchial tree or from the upper aerodigestive tract [60] . As specified above, in situ squamous cell carcinoma may exhibit a quite similar appearance ( Fig. 2.32 ).

z z Squamous carcinoma cells with strong nuclear hyperchromasia in combination with a tendency toward pyknosis and areas of cleared nucleoplasm are difficult to distinguish from benign squamous cells with severe actinic changes ( Fig. 2.13 ). Additive DNA ploidy analysis will be of little help in assessing malignancy since radiotherapy can cause major quantitative and structural alterations to the genome. z z Squamous metaplasia with reactive-reparative changes and true dysplastic squamous metaplasia generally comprise, although to a lesser degree, nuclear atypia and smaller cells ( Fig. 2 z z Regeneration and repair within the epithelium of the respiratory tract may produce large atypical single cells mimicking nonkeratinizing SCC; however, differential diagnosis problems of proliferative bronchial/alveolar lining cells are much more accentuated against adenocarcinoma.

z z Proliferating histiocytes and fibroblasts shed from a florid granulomatous process into the bronchial system may look like poorly differentiated carcinoma cells, in particular in specimens with a tendency toward dense epithelioid clustering of the mesenchymal cells. Immunocytochemical positivity for CD68 and negativity for cytokeratins indicate a histiocytic origin of morphologically equivocal cells.

z z An appropriate panel of antibodies proved to be helpful in determining a definite diagnosis: pulmonary squamous cell carcinoma stains positively for CK5/6 [30, 51] . CK20 and CK7 are rarely expressed in malignant squamous cells of the lung, and TTF-1 and leukocyte antigen are never expressed.

z z The following primary and secondary neoplasms should primarily be included in the differential diagnosis of nonkeratinizing SCC: − Poorly differentiated adenocarcinomas of the lung show positive immunoreactivity for CK7 and TTF-1 [30] . However, CK7 has a low specificity since it is also expressed in pulmonary SCC, in large-cell carcinoma NOS (not otherwise specified), in large-cell neuroendocrine carcinoma, and in a variety of adenocarcinomas secondary to the lung [51] . − Transitional cell carcinoma demonstrates immunopositivity for CK7 and CK20. − Mesothelioma of the undifferentiated epithelial or sarcomatoid variant. Immunocytochemistry, see Sect.

3.2.1.3, "Additional Analyses," p. 262. − Melanoma is characterized by positive immunostaining for melanoma-specific antigens (e.g., Melan A, HMB45). − Large-cell malignant lymphoma is determined by positive immunostaining with antibodies against leukocyte antigen and lymphocytic markers.

A minimal marker panel of p63 and TTF-1 has been proposed, differentiating pulmonary squamous carcinomas from pulmonary adenocarcinoma, while other markers such as CK5/6 or CK7 could be added [119A] . However, many types of nonpulmonary adenocarcinomas may be positive for CK5/6 [20] . 

General Comments z z The frequency of adenocarcinoma is increasing worldwide. The increase in lung cancer in women is attended by a parallel increase in adenocarcinomas. Females are thought to be predisposed to adenocarcinoma due to a specific determination of the pulmonary epithelial cells to inhaled cigarette smoke [55, 87, 105] .

z z Adenocarcinoma is a malignant epithelial tumor with glandular differentiation, with or without mucin production. Adenocarcinoma is further classified histologically into the main subtypes: acinar, papillary, solid, and bronchioloalveolar. However, a mixture of the four patterns is common and the mixed subtype is most frequently encountered in routine practice. z z Adenocarcinomas are usually situated more peripherally in the lung compared to SCCs. Thus, adenocarcinoma may shed small numbers of cells or no cells at all into the bronchial system. The yield of exfoliation mainly depends on tumor site and tumor size. z z The differences in cytologic presentation of the varied subtypes of adenocarcinoma have been studied by numerous authors [43, 97, 109] . The studies mainly focused on the cytologic properties and differential diagnosis challenges of bronchioloalveolar carcinoma related to different sampling modalities [85, 104, 108, 110, 116] . 

A number of studies have been published over the last decades as well as in recent years, contributing to the cytological diagnosis and differential diagnosis of BAC [43, 85, 97, 104, 108, 110, 116] . However, for many cases it will not be possible to establish a final diagnosis. The round to oval nuclei are extremely uniform in size, but nuclear grooves are commonly observed together with occasional cytoplasmic invaginations. The chromatin is finely granular or powdery and evenly distributed.

Chapter 2  Respiratory Tract and Mediastinum z z CK7 provides high sensitivity for primary pulmonary adenocarcinomas, but the marker has a low specificity .

DNA ploidy, cytophotometry, and molecular genetics have been discussed in Sect. 2.1.4.3, "Additional Analyses", p. 115. (Fig. 2.47 )

Undifferentiated large-cell pulmonary carcinoma is composed of highly malignant anaplastic cells that lack morphologic features of squamous or glandular differentiation. The tumor comprises about 10% of all lung carcinomas.

Diagnosis of large-cell undifferentiated carcinoma does not exclude a tumor with focally more differentiated areas of specific morphology whose cells are currently absent in the cytologic specimen.

Preponderance of very large single cells. Cellular grouping occurs in a syncytial modality.

The N/C ratio is high. The nuclear contour is highly abnormal, cleaved, and lobulated. The chromatin is irregularly dispersed exhibiting strands and clusters. The parachromatin may be hyperchromatic or lucid. The nucleoli are large and pleomorphic and their number varies from cell to cell. 

Differential diagnosis considerations are similar to those of poorly differentiated SCC and poorly differentiated adenocarcinoma including: metastatic undifferentiated carcinoma, pulmonary invasive mesothelioma (undifferentiated epithelial or sarcomatoid type), amelanotic melanoma, sarcoma, large-cell lymphoma, cellular alterations due to chemotherapy and irradiation.

Other tumor entities presenting with large tumor cells are discussed in subsequent sections of this chapter.

Adenosquamous carcinoma is a histologically heterogeneous neoplasia due to dual differentiation into squamous cell carcinoma and adenocarcinoma.

Adenosquamous carcinoma is generally easily recognized as malignant neoplasia in cytologic routine practice, but proper subtyping is often not possible: the cytological diagnosis of this tumor entity requires unequivocal evidence of malignant keratinized squamous cells and mucin-secreting cells of the adenocarcinoma type.

General Comments z z Small-cell carcinoma belongs to the group of neuroendocrine tumors of the lung (see Sect. 2.2.3, p. 149). A majority of small-cell carcinomas demonstrate neuroendocrine differentiation by immunocytochemical staining for neuroendocrine markers (see "Immunocytochemistry" below), both on tissue sections and cytologic specimens [72] .

z z Small-cell carcinoma is a highly aggressive tumor with a high mitotic activity; they are known to have a poor clinical course [13, 32, 119] .

z z Cytology, especially FNAB, has proved to be an excellent method to distinguish small-cell carcinoma from other lung cancers [15, 29] . Fundamental and specific cytologic features of small-cell carcinoma include cellular/nuclear molding and fine, smudgy chromatin.

Caution z z We emphasize a careful evaluation of all respiratory cytologic specimens from patients with clinically suspected lung cancer . In so doing, a very few wellpreserved individual and grouped small undifferentiated tumor cells can be detected and generally allow a correct diagnosis (Fig . 2 .48 ) . z z Nuclear hyperchromasia and dyschromasia in small carcinoma cells appear deep blue to black and dark pink to bright pink, respectively . z z Tumor cells of small-cell carcinoma entrapped in blood may be obscured and easily missed .

z z Dense clusters of hyperplastic basal cells entrapped in thick blood masses may be misinterpreted as tumor cell clusters from a small-cell carcinoma of the oat cell type .

The 1981 WHO classification scheme differentiated three subtypes of small-cell carcinoma: oat cell carcinoma, smallcell carcinoma of the intermediate cell type, and combined small-cell carcinoma [128] . Later on, the terms "oat cell carcinoma" and "intermediate cell type" were dropped. The 1999 and 2004 WHO classification [119] propose the terms:

(1) "Small-cell carcinoma" to be used for tumors with a pure small-cell pattern lacking a non-small-cell component. (2) "Combined small-cell carcinoma" for tumors that show a mixture of small-cell carcinoma and any other non-smallcell component [132] .

For cytodiagnostic purposes, it is highly recommended to remember the two small-cell types: oat cell and intermediate . These two cell types contribute to diversified differential diagnostic considerations .

Microscopic Features [6, 96, 132] The cytologic pattern and cellular morphology are pathognomonic in such a manner that a determinate diagnosis should be possible even on single cells.

(1) Cytologic appearance affected by sampling and preparatory modalities: Immunocytochemical stains for p63 and TTF-1 were shown to reliably distinguish between small-cell carcinoma of the lung and small-cell SCC [59] . 

There are various reasons for a biphasic small-cell / large-cell tumor pattern: 

This tumor group comprises neoplasms that are probably of bronchial gland origin. The morphology of these tumors is similar to their counterparts in the salivary glands and in other organs. They are described in more detail in Sect. 5 Adenoid cystic carcinomas usually arise in large bronchi and in the trachea. Distinction from well-differentiated pulmonary adenocarcinoma and mucin-producing adenocarcinomas with a histologically pronounced cribriform architecture may be difficult [21, 27, 77, 107] . A pure epithelial component can lead to a misdiagnosis of carcinoid tumors.

Mucoepidermoid carcinoma usually arises in the periphery of the bronchial tree. An admixture of neoplastic squamoid cells and mucin-containing tumor cells together with variable amounts of extracellular mucus will definitely provide a correct diagnosis. However, epidermoid features of the malignant squamous cells may be poor and are likely to be overlooked; their cytoplasm may be dense or finely vacuolated. z z Low-grade mucoepidermoid carcinoma is composed of a monotonous tumor cell population with lack of unambiguous evidence of malignancy; the diagnosis will more frequently be suggestive than definite. Differential diagnoses include mucous gland adenoma, bronchioloalveolar carcinoma, mucinous adenocarcinomas (primary and metastatic), among others [77, 99, 107] . z z High-grade mucoepidermoid carcinoma is difficult to separate from adenosquamous carcinoma, as keratinized epidermoid cancer cells frequently occur.

The group of salivary-gland-type carcinomas further includes epithelial-myoepithelial carcinoma.

Clear cell carcinoma is composed of large polygonal tumor cells with clear foamy cytoplasm whose glycogen content is highly variable. It is important to emphasize a number of secondary lung lesions that highly resemble pulmonary clear cell carcinoma: Extrapulmonary clear cell carcinoma may be situated in the kidney, thyroid, salivary gland, female genital organs, or breast. Benign clear cell tumor of the lung -sugar tumor -has to be excluded as well.

Lymphoepithelial carcinoma is an undifferentiated epithelial neoplasia of the large-cell type associated with prominent benign lymphoid infiltration. This tumor entity is typically located in the nasopharynx and occurs extremely rarely in other sites including the lung. The cytomorphologic features of this tumor are provided in Sect. 8.7.3, p. 568. Pulmonary lymphoepithelioma-like carcinoma has to be distinguished from benign and malignant lung disorders that are accompanied by pronounced lymphatic hyperplasia such as granulomatous disorders (abundant lymphocytosis and activated histiocytes that mimic carcinoma cells), malignant lymphoma (large-cell blastic type accompanied by benign lymphoid hyperplasia), melanoma, or sarcoma [19] .

Sarcomatoid carcinomas are poorly differentiated non-smallcell lung cancers that are accompanied by spindle cells, giant cells (or a mixture of both cell types), or a sarcomatous component [1, 74, 75, 100, 119] . [75] . If immunostaining for cytokeratins is negative, separation from true sarcoma is practically impossible from cytomorphology alone. 

Sarcomas rarely occur in the lung and a diagnosis from cytology is rather ambivalent. They are more likely encountered in fine-needle aspirates than in exfoliative cytologic samples; stromal tumors rarely exfoliate their cells into the bronchial tree. Only a few cases are on record in the literature, leiomyosarcoma [3, 84, 129] , chondrosarcoma [71] , synovial sarcoma, fibrosarcoma [66] , and malignant fibrous histiocytoma [35, 46] . Leiomyosarcoma is most frequently reported. Hummel and coauthors recently reviewed a large number of pulmonary spindle cell and mesenchymal lesions in transthoracic FNABs with respect to cytomorphologic features, differential diagnosis, and pitfalls [47] ; Wakely studied the features and limitations of FNAB in the analysis of pulmonary spindle cell lesions [121] .

Malignant germ cell tumors of the lung are extremely rare. In suspicious cases, an anaplastic primary lung carcinoma should always be excluded.

As known from other body sites (e.g., mediastinum, retroperitoneum), metastatic germ cell neoplasms to the lung may be solely composed of mature tumor elements after successful chemotherapy and radiotherapy of the remote primary tumor. 

z z The lung is the most common site of metastatic tumor implants. Approximately 50% of all metastatic tumors to the lung shed their cells into the pulmonary airways [61] . Numerous metastatic neoplasms mimic primary lung cancer morphologically, clinically, and on imaging studies. Cavitation, interstitial growth, and an alveolar wall-lining pattern may be marked in varied secondary tumors. z z Adenocarcinoma is by far the most common metastatic tumor detected in exfoliative bronchial specimens. Among these, adenocarcinoma from the colon and breast are the most frequently encountered cancers, both in the past and in current practice [4] . Other relatively frequently encountered metastases and invasive lung tumors from adjacent sites are renal cell carcinoma, transitional cell carcinoma, squamous cell carcinoma, malignant melanoma, and malignant lymphoma.

z z Immunocytochemical studies are extremely helpful to establish the primary tumor site for the majority of suspected metastatic tumors with indistinct cytologic findings [86] . Further help may be provided by a positive clinical history and correlative studies with relevant histologic material from the same patient. z { The nuclei are irregular including deep grooves, the chromatin is fine and pale, and nucleoli may be inconspicuous. In addition, many cases will reveal a singlefile tumor cell arrangement. Thus, the resemblance to bronchioloalveolar carcinoma is striking, as it is to other secondary tumors that exhibit similar nuclear features such as renal cell carcinoma, papillary thyroid carcinoma, and papillary transitional cell carcinoma.

Immunocytochemistry: Breast carcinoma (hormone receptors +) and lung adenocarcinoma (TTF-1+) show an opposite immunoprofile (please see "Cautions", p. 149). (Fig. 2.60) Lung metastases of colonic adenocarcinoma are commonly associated with small and large tight cell clusters. Immunocytochemistry: CDX2 and CK20 positivity and CK7 negativity are reliable indicators for metastatic colonic carcinoma.

Cells of poorly differentiated urothelial carcinoma metastatic to the lung may look like those exfoliating from a poorly differentiated squamous cell carcinoma.

z { Both tumor entities may contain large cells with pleomorphic nuclei, large nucleoli, and dense cyanophilic cytoplasm; the latter may show vague concentric lamellation. Pronounced necrotic debris raises suspicions of transitional cell carcinoma.

Immunocytochemistry: An immunocytochemical profile including positivity for CK7, CK20, and CK13 raises suspicions of transitional cell carcinoma. CK20 usually show no positive reaction on malignant squamous cells of primary lung origin.

This tumor is composed of rather monomorphic mediumsized to large cells showing a characteristic round nucleus, a single pronounced nucleolus, and evenly distributed granular chromatin. The tumor cells are arranged in compact and regular sheets and clusters.

Immunocytochemistry: Positivity for specific prostatic cellular antigens (e.g., PSA) helps to provide a final diagnosis. (Fig. 2.61) Pigmented melanoma should raise no diagnostic problems except in rare cases of carcinoid tumors that exhibit nuclear polymorphism and melanin production. However, nonpigmented melanoma may be difficult to differentiate from poorly differentiated squamous cell carcinoma, poorly differentiated adenocarcinoma, and undifferentiated carcinoma of the lung. All these tumors are characterized by large cells, pleomorphic nuclei, huge nucleoli, clumped chromatin, and cytoplasm of varying shape, size, and structure. Absence of cell clustering is pathognomonic for large-cell neoplasms.

Immunocytochemistry: Reactivity for melanoma-typical markers (HMB-45, Melan A) together with a strong positivity for S100 are indicators for the presence of amelanotic melanoma.

Pleural mesothelioma is a diffusely spreading tumor involving primarily parietal and visceral surfaces of the thoracic cavity and lung. Mesothelioma, mainly of the sarcomatoid type, may infiltrate beyond the pleura visceralis into the lung parenchyma. Infiltrates may mimic a peripheral lung tumor and can be investigated by FNAB. Mesothelioma cells may rarely be encountered in exfoliative samples from the bronchial system.

Immunocytochemistry: Calretinin-positive epithelioid tumor cells that show negative reactivity for TTF-1 raise high suspicions of a mesothelioma invading the lung.

A distinct tendency exists for sarcomas to metastasize into the lung parenchyma. Spindle cell pulmonary carcinoma, undifferentiated carcinoma, and mesothelioma of the sarcomatoid type have to be excluded by immunocytochemical testing (Fig. 2 z z Immunocytochemical reactivity for neuroendocrine markers (chromogranin, synaptophysin, and CD56) acts as an indicator for neuroendocrine differentiation. Immunostaining reveals no crucial differences between the four subtypes of neuroendocrine tumors.

z z Carcinoids typically appear as nodular exophytic lesions protruding into the bronchial lumen, but tumor cells are rarely observed in sputum and bronchial secretion due to the intact covering mucosa. In contrast, carcinoids generally provide a large number of cells in specimens sampled by brushing and fine-needle aspiration. z z Neuroendocrine differentiation has been found to be an attribute not only of NET but also of a proportion of nonsmall-cell lung carcinomas. Detection of focal neuroendocrine features in the latter depends on a spectrum of technical approaches and biological properties (antibodies used, nature of tissue specimen, etc.) [12, 112] . [13, 78, 80] 

Sputum probes that contain typical carcinoid cells may likely be attended by pronounced cell detritus and necrosis derived from the traumatized mucosal surface area and not from the tumor parenchyma itself .

z z A solid epithelial component of adenoid cystic carcinoma that is composed of small monomorphic cells may be mistaken for carcinoid cells. Cells of adenoid cystic carcinoma are immunocytochemically negative for neuroendocrine markers. z z Low-grade non-Hodgkin lymphoma may mimic carcinoid tumors in cases exfoliating numerous isolated monomorphic tumor cells (Fig. 2.56 ). z z Metastases of monomorphic small-cell adenocarcinomas (e.g., breast carcinoma) exhibiting fine granular chromatin, inconspicuous nucleoli, and variably granular cytoplasm must be eliminated. Immunocytochemically, hormone receptors are not expressed in cells of carcinoid tumors, but cells of breast carcinoma may coexpress neuroendocrine markers. [63] . However, pulmonary paraganglioma is extremely rare and cytokeratins are not expressed by use of immunocytochemistry. [52, 53, 69, 80, 123] (Fig. 2.67 

Clear positivity with one neuroendocrine marker is sufficient for a definite diagnosis of LCNC. Synaptophysin seems to be the perfect neuroendocrine marker for this particular tumor entity. Synaptophysin is highly specific and more sensitive than chromogranin [44, 123] . About 50% of the large-cell neuroendocrine carcinomas show nuclear positivity for TTF-1 antigen [53, 113] .

z z LCNC comprising pronounced nucleolar polymorphism and large cytoplasm may be confused with poorly differentiated primary lung carcinoma of squamous or glandular origin [58] (Fig. 2.67 ). z z Rarely, LCNC can be misdiagnosed as small-cell carcinoma; even so, single-file cell arrangement, small nuclear size, nuclear molding, and absence of nucleoli are important differential features typically occurring in small-cell carcinoma [58, 130] .

z z Large-cell-type prostatic carcinoma (large nucleoli, finely granular chromatin, cytoplasmic similarity) may mimic LCNC. Immunocytochemical reactivity for prostate-specific markers and negative immunostaining for neuroendocrine antigens exclude LCNC, and vice versa.

Fifty percent of LCNCs show immunocytochemical posi tivity for TTF-1 . Distinction from poorly differentiated pulmonary adenocarcinoma may be difficult .

z z Pulmonary tumorlets are evidenced to originate from pulmonary Kulchitsky-type cells. Therefore, tumorlets can be defined as benign localized neuroendocrine cell proliferations looking like tiny peripheral carcinoids (less than 5 mm in diameter). Tumorlets are frequently associated with neuroendocrine cell hyperplasia in the adjacent bronchiolar mucosa [94] . z z Nodules with an exceptional protrusion into the bronchial lumen are visualized by endoscopy and may be followed by brushing or transbronchial FNAB. z z Tumorlets are usually composed of spindle cells or epithelial-type cells; therefore, their morphology is indistinguishable from typical or atypical carcinoid tumors. z z The cell pattern of tumorlets can occasionally mimic small-cell carcinoma, well-differentiated adenocarcinoma, or a nonepithelial malignant neoplasm [5, 106] . However, the regularity of the tumorlet nuclei and a very low mitotic activity should exclude malignancy. 

Two examples of intrapulmonary hamartoma presenting with different tissue components. 

Two examples of keratinizing SCC are presented from a sputum probe and from a fine needle aspirate (see also Fig. 2.34B) . Note the striking similarity of the crescent carcinomatous cluster compared to the benign epithelial cluster (arrow): identical cellular and nuclear shape, identical nuclear texture and color, and an identical cytoplasmic structure. A major difference however, is observed regarding cellular arrangement, cellular size, and nucleoli (bronchial brushing, direct smear, Pap stain, high magnification). Fig. 2.48A , B Small-cell carcinoma: paucicellular exfoliative sample. The cells depicted in these two images come from the same sputum probe (Pap stain). The examples emphasize the particular importance of careful microscopic screening in patients with small-cell carcinoma. A Very low magnification displays a single tumor cell cluster (arrow) that meets all criteria of small-cell carcinoma. B High magnification demonstrates a few single carcinoma cells (arrows) and a dyad of small carcinoma cells (arrowhead) amid benign lymphocytes. Attention should be paid to the size and chromatin texture of the neoplastic cells as compared to lymphocytes. Tumor cells of small-cell carcinoma (mainly of the oat cell type) occurring completely dissociated in a smear from a bronchial aspirate. Therefore, distinguishing between small-cell carcinoma and malignant lymphoma is difficult. Still, absence of unequivocal lymphoid cells, absence of cytoplasmic rims, and absence of nucleoli in the majority of the nuclei favor the diagnosis of small-cell carcinoma (direct smear, Pap stain, higher magnification).

Classic appearance of adenoid cystic carcinoma: three-dimensional clusters composed of small monomorphic tumor cells surrounding cores of pinkish hyaline material (bronchial aspirate, direct smear, Pap stain, lower magnification).

A 63-year-old man presented with a tumor in his right lung. Antecedent exfoliative cytologic and histologic investigations yielded no conclusive diagnosis. Transbronchial FNAB revealed a heterogeneous cell pattern composed of metaplasia-like sheets of immature squamous cells interspersed with mucinous glandular cells and goblet cells (arrows) (direct smear, Pap stain, lower magnification). A few keratinizing squamous cells were also present (not shown). Cytologic diagnosis of a mucoepidermoid carcinoma was later verified with histology.

A 63-year-old man presented with a diffuse infiltrate in his right lung. Sputum cytology revealed a neoplasia consisting of atypical monomorphous cells characterized by conspicuous nucleoli, and mostly ill-defined cytoplasm; cytoplasmic vacuolization is overt, unlike the fuzzy granularity (Pap stain, high magnification). Cytologic differential diagnosis: Malignant non-Hodgkin lymphoma, carcinoid tumor, and small-cell carcinoma of intermediate cell type. Comments: The latter diagnosis seems rather unlikely due to the nuclear monomorphism, unfitting chromatin texture, and cytoplasmic features. Clarifying the histogenesis of this tumor requires immunocytochemical workup (not performed by cytology because of technical problems).

Tissue diagnosis (open lung biopsy): Follicular non-Hodgkin lymphoma, grade 2. Fig. 2.58 Hodgkin lymphoma. A female patient with a positive history of Hodgkin lymphoma; clinical findings suggest tumor dissemination into the lung. Numerous distinct Reed-Sternberg cells (arrow) and mononuclear Hodgkin cells were seen in the first sputum sample (Pap stain, higher magnification). Cytologic diagnosis: Hodgkin lymphoma. Comment: The diagnosis of Hodgkin disease was easy in this case due to patient's history. However, distinguishing RSH cells from cells of anaplastic carcinoma would be very difficult without an appropriate clinical history.

A 72-year-old woman with positive history of breast carcinoma (lumpectomy and irradiation 12 years before) presented with a tumorous lesion in her right lung. A Bronchial aspirates and bronchial brushings showed numerous isolated and clustered tumor cells consistent with a monomorphous well-differentiated adenocarcinoma (direct smears, Pap stain, high magnification). An appropriate immunopanel is essential in order to assess the primary site of the neoplasia (lung cancer versus metastasis of breast carcinoma). B Nuclear positivity for estrogen receptors (Pap-prestained direct smears). C Negative immunoreactivity for TTF-1 (Pap-prestained direct smears). Cytologic diagnosis: Selected immunostains established correct diagnosis of breast cancer.

A 53-year-old man presenting with lung disorders and a positive history of colonic carcinoma. A Compact cell clusters from a poorly differentiated adenocarcinoma were encountered in bronchial brushings (Pap stain, high magnification). B Positive immunostaining for CK20 proved helpful in determining a definite diagnosis of metastatic colonic carcinoma. Fig. 2.61A, B Malignant melanoma. A 91-year-old man presented with a nodular lesion in the upper lobe of his left lung, there was no further information available. A Bronchial brushing revealed mainly isolated large neoplastic cells exhibiting vulnerable vacuolated and granular cytoplasm. A macrophage (arrow) shows coarse granular cytoplasmic inclusions suspicious of melanin, but hemosiderin cannot be excluded by routine staining methods (direct smear, Pap stain, high magnification). B Positive immunostaining for HMB-45 (Pap-prestained direct smear). Cytology: Cytomorphologic features and suspected melanophores favor the diagnosis of malignant melanoma (versus another undifferentiated nonepithelial tumor or anaplastic largecell carcinoma). Immunocytochemical work-up provided the correct diagnosis. (False) cytologic diagnosis: Poorly differentiated nonkeratinizing squamous cell carcinoma. Comment: the cytologic diagnosis was established due to the cellular pleomorphism, coarse granular chromatin, and streaming pattern (we failed to perform immunocytochemical studies). General Comments z z At our institution, BAL fluid processing has followed standardized rules based on 15 years of experience with a total number of roughly 6,000 specimens. More than half of these BAL samples have been adequate for differential cell count and determination of the lymphocyte subset. Adequacy of the specimens was determined by the volume of the aspirate, by the amount of bronchial/bronchiolar cell admixture, by total cell count, and/or by the limitation of analyses as requested by the attending physician. The nonadequate specimens underwent routine screening for cellular composite, tumor cells, quality of histiocytes/ macrophages, dust particles, virus-induced cell changes, and organisms. 

The BAL fluid is transported and processed as quickly as possible, i.e., within 6 h after sampling. Specimens from the hospital-based lung department are supplied immediately after completing the endoscopic investigation. BAL samples from county hospitals and community-based clinicians are supplied individually or by a pick-up service, both within 6 h. In this setting, the samples are delivered in native condition. Each analysis is announced at least 2 h before the sample arrives at our laboratory.

1. The first aspirate, the contents of the bronchus segmentalis and bronchioli, is referred separately to our cytology laboratory. This sample generally has cellular and mucus content of the bronchial/bronchiolar system and is suitable for measuring the adequacy of the BAL specimen. 2. Delay of the procedure [14] . Samples arriving at the laboratory too late in the evening for complete routine processing are centrifuged with the sediment transferred to a suitable cell medium (we use MEM HBS without l-glutamine, Amimed BioConcept, Allschwil, Switzerland). Cell suspensions can be stored in the refrigerator (4°C) and all routine BAL examinations are reliable for at least 24 h. 3. Routine processing of BAL fluid and basic evaluation.

The principle steps are described as performed at our laboratory. Technical details and conditions tailored to our particular needs are disregarded. − Amount and gross appearance of the lavage fluid obtained are noted. Portions of the recovered instillation for supplemental noncytologic analyses, such as culture, viral analyses, biochemical tests, etc. have already been submitted to specialized laboratories by the endoscopist. − The total amount of liquid is centrifuged (2800 rpm, 10 min). The supernatant is decanted by aspiration and may be deep-frozen for long-term storage. It can be used for subsequent noncellular analyses. − Mucus from the sediment is liquefied by adding Shandon Mucolexx TM (Thermo Fisher Scientific Inc., Waltham, MA, USA); individual exposure is up to 10 min. Afterwards, the resuspended cell pellet with the above-mentioned cell medium (2-3 ml), is again centrifuged (4000 rpm, 2 min). − Total cell counts are made in a Neubauer Cell Chamber. The result is reported per liter of recovery fluid. − For differential cytology, a routine air-dried smear is stained according to the May-Grünwald-Giemsa (MGG) staining procedure. Differential cytology includes the percentage of macrophages, lymphocytes, neutrophils and eosinophils, mast cells, and plasma cells.

Pay attention to the fact that mast cell granules are faintly or not at all stained by the DiffQuik staining procedure .

− Two wet-fixed smears are routinely stained with the Papanicolaou method (Pap) and screened for entire cellular composite, tumor cells, quality of histiocytes/ macrophages, dust particles, virus-induced cell changes, and organisms. Further slides (wet fixed or/and air-dried) are prepared as simple smears or by cytocentrifugation according to the clinical requirements. 

Lymphocyte subpopulations can be identified using immunocytochemical methods on wet-fixed and air-dried cytospin preparations or alternatively by fluorescence-activated cell sorting (FACS ® Becton Dickinson, San Jose, CA, USA), a specialized type of flow cytometry. The latter method, which we prefer, is based upon the specific light scattering (Fig. 2.68A) Differing normal values for differential cytology have been reported in the literature. Guidelines of a Task Group of the European Society of Pneumology recommend the following values as normal [29] : Macrophages > 80%. Lymphocytes ≤ 15%. Neutrophils ≤ 3%. Eosinophils ≤ 0.5%. Mast cells ≤ 0.5%.

The values can be applied to both cytocentrifuged specimens and direct smears.

z { Macrophages are uniform, the nuclei exhibit a characteristic kidney shape, bland chromatin, and a cyanophilic /basophilic cytoplasm. Cytoplasmic vacuoles and particle inclusions are rare. Multinucleation is a normal finding in a small percentage of macrophages. (Fig. 2.68B) Total cell counts are markedly increased in otherwise healthy smokers, in the first instance due to the macrophage cell component [16] . Macrophages may show up as clearly increased and irregular cytoplasm bearing round inclusions (MGG stain: blue-black). These so-called smoker's inclusions consist of ingested particles from the inhaled smoke [17, 34] . The percentage of lymphocytes is reduced and that of granulocytes is the same as in nonsmokers.

The determination of the lymphocyte subsets, T-helper cells (CD4), and T-suppressor cells (CD8) may be of substantial help in the diagnostic management of patients presenting with alveolar lymphocytosis. Changes in the CD4/CD8 ratio are quite typical for certain peripheral lung diseases. The CD4/CD8 ratio of the normal lymphocytic population in BALs of healthy individuals and nonsmokers achieves a median value of 2.0 (range, 1.1-3.5), that of smokers is halved [33] .

Caution z z Normal cellular composite of the BAL definitely excludes active sarcoidosis, active extrinsic allergic alveolitis, common and eosinophilic pneumonia, alveolar hemorrhage syndrome, and alveolar proteinosis . z z Abnormal components in a BAL that are interspersed between numerous normal bronchial epithelial cells call for careful diagnostic interpretation . These elements may originate exclusively from the bronchial and bronchiolar system .

Few pathologic lung conditions can be diagnosed by BAL alone. However, in many cases BAL serves as an important adjunct leading to a conclusive diagnosis in the context of clinical, radiologic, and biochemical findings. For other clini cal entities, BAL cannot replace lung biopsy, hence a supplemental histologic evaluation is unavoidable. A synopsis of the most significant findings in BAL specimens is provided in Table 2 .3.1, below.

The cytologically most important lung disorders are subsequently focused in connection with diagnostic findings in bronchoalveolar lavage and differential diagnoses. For detailed information, we refer the readers to distinguished books and relevant publications [8, 10, 12, 37] . Several literature reports related to the various entities are cited.

Sarcoidosis is a multisystem disorder commonly arising in young adults, characterized by noncaseating granulomas with typical cellular features. The cause of the disease is still unknown. Granulomas most often appear in the lungs or in the lymph nodes, but virtually any organ can be affected. The clinical course generally varies and ranges from an asymptomatic disorder to chronic debilitating disease. 

Berylliosis may show high CD4/CD8 ratios as well. Increased ratios are also valid for extrinsic allergic alveolitis, nonspecific interstitial pneumonia, idiopathic pulmonary fibrosis, pneumoconiosis, and other disorders. However, the nonlymphoid cell features differ from those in sarcoidosis.

Extrinsic allergic alveolitis (EAA) is an immunologically mediated interstitial lung disease. Many airborne organic antigens in the form of fungal spores, bacteria, aerosolized proteins (predominantly from birds) can cause hypersensitivity pneumonitis after repeated inhalational exposure [26] . A wide variety of hypersensitivity lung diseases with their correspondent antigens are tabulated in Costabel's BAL Atlas [10] . Many people who are exposed to allergens and become sensitized can remain asymptomatic but may show characteristic abnormal BAL morphology. Ongoing alveolitis may progress in chronic illness with evidence of lymphocytic alveolitis, granulomatous reaction, and finally fibrotic interstitial changes.

z z EAA is associated with the highest total cell count and the highest number of lymphocytes in BAL compared with other interstitial lung disorders. z z Abnormalities in the bronchoalveolar lavage fluid cell counts are almost always seen in patients with EAA according to different phases of the disease: at an early stage of allergen exposure the number of neutrophils increases and returns to a normal range within 1 week. The pathognomonic BAL findings become apparent in the subacute and chronic phase of the disease. z z Mast cells have been reported to occur in higher rates in BAL of EAA compared to other interstitial lung diseases [25, 38] . 

These disorders encompass an inhomogeneous group of inflammatory immune diseases with a progressive course, involving connective tissue, joints, blood vessels, and other -Cytotoxic reaction may be pronounced to such a degree that cellular atypia is mistaken for malignancy organs with alternating intensity. The lung is not always affected. BAL findings are similar to those in idiopathic pulmonary fibrosis. Lymphocytosis seems to be more common in immune conditioned inflammatory processes indicating a more favorable prognosis. Specialized sources in the literature should be consulted for further information [10, 31, 42 , and others]. Eosinophilic lung diseases are characterized by pulmonary eosinophilia that is an accumulation of abnormal quantities of eosinophils in air spaces and interstitial tissue of the lung. [10] z z Infectious agents: Pulmonary eosinophilia includes parasitic infections, particularly ascariasis in children. Löffler syndrome is frequently associated with helminthic infections, but about one-third of the cases are idiopathic. Fungal pulmonary eosinophilia is in most cases caused by an aspergillus-associated hypersensitivity respiratory disorder referred to as allergic bronchopulmonary aspergillosis. z z Drugs: Crack, cocaine, and heroin inhalation have been reported to induce acute eosinophilic lung disorder [61] . Churg-Strauss syndrome (CSS) is characterized by clinical and pathological manifestations, which separate the condition from other eosinophilic disorders: blood eosinophilia, asthma, and organ-specific disorders effected by vasculitis; the diagnostic relevance of antineutrophil cytoplasmic autoantibodies (ANCA) is under debate. Histopathological findings include epithelioid granuloma, tissue eosinophilia, and necrotizing vasculitis [23] . Marked eosinophilia in BAL fluid is a hallmark of CSS. In contrast, Wegener granulomatosis is not associated with asthma bronchiale and exhibits mild eosinophilia together with a definite higher percentage of neutrophils [53] .

z z Hypereosinophilic syndrome is not associated with vasculitis.

z z Idiopathic acute and chronic eosinophilic pneumonia [15, 43] : Alveolar eosinophilia is generally combined with peripheral blood eosinophilia. The proportion of alveolar eosinophiles always predominates in contrast to other pneumonic disorders such as ARDS or bacterial pneumonia. Chronic eosinophilic pneumonia is almost always associated with the alveolar presence of plasma cells, but the neutrophil count is in normal range (in contrast to Wegener granulomatosis). Chronic idiopathic eosinophilic pneumonia is very sensitive to corticosteroids. Inhalation of asbestos dust can induce variable occupational diseases such as pulmonary fibrosis (asbestosis), malignant mesothelioma, benign pleural fibrotic disorders, and bronchial carcinoma. Therefore, asbestos use has been banned in most developed countries but exposure still occurs, and asbestosis deaths are not expected to decrease sharply in the United States during the next couple of years [2] . z z Pathogenesis, including associated immunological mechanisms of asbestosis, quantitation using the asbestos body filtration technique, and its clinical implication are highlighted in Costabel's atlas [10] . 

Early reaction to asbestos inhalation may consist of a mild lymphogranulocytic inflammatory process. Early asbestosis induces a marked inflammatory process that is easily recognized in BAL specimens. Ongoing development of the fibrotic process results in a decrease in the percentage of inflammatory cells. Lymphocytosis may reach 15% with an increased CD4/CD8 ratio. Lymphocytosis is presumed to be associated with a less aggressive course [10, 48, 65 ]. (Fig. 2.75 )

True asbestos bodies have to be distinguished from pseudoasbestos bodies. The latter are inhaled fibers with a mineralogical composition unlike asbestos but a related iron-containing coat. Such fibers can be made up of carbon, aluminum, glass fibers, and other biological and artificial fiber types [10] .

z { Compared to classic asbestos bodies, pseudo-asbestos bodies lack the slender beaded shape, and the smooth surface of the terminal protrusions. The elements are more polymorphous and plump.

The term "ferruginous body" is commonly applied to asbestos bodies but can be used for each iron-coated fusiform element regardless of the nature of the central fiber .

Silicosis (also known as grinder's disease) is caused by inhalation of crystalline silica (quartz crystals) dust and characterized by marked inflammation and scarring nodular lesions in the upper lobes of the lungs. 

These are mixed forms of pneumoconioses caused by inhalation of coal dust, stone dust, and other minerals in which the degree of lung injury depends on the composition of the dust and the amount of quartz crystals.

z { Carbon particles appear as dark-brown (MGG stain) to black (Pap stain) large and polyhedral cytoplasmic inclusions in macrophages; the elements occur singly or densely clustered. Coal dust inclusions do not stain with the iron-staining method. Quartz crystals, coated pseudo-asbestos fibers, and sporadic asbestos bodies may be encountered as well.

Metal workers are usually exposed to mixed dust inhalation; accordingly, the macrophages may strongly vary in their morphologic aspect. Fully mixed inclusion patterns are referred to as anthraco-sidero-silicosis: Welder's Lung (Fig. 2.77 ) Welder's lung is a specific presentation of pulmonary siderosis caused by smoke inhalation during welding. Welding dust usually contains metallic iron and iron oxide, which are inert to the human lung. Large amounts of iron dust are ingested in macrophages and settle in lung parenchyma without distinct fibrosis unless crystalline silica is also present [28, 56] .

z z Ultrastructural analysis with electron microscopy provides a more definitive diagnosis than cytomorphology alone: whorled myelin-like figures that resemble surfactant ( Fig. 2.79 ). They are usually accumulated in the background of the smears, less frequently intracytoplas- In patients with ambiguous imaging and clinical results, further diagnostic procedures may be needed such as surgical lung biopsies in order to confirm the diagnosis on tissue sections [5, 68] . The diagnostic impact of BAL cytology is agreed to be low.

Histology: Tissue sections reveal Langerhans cell granulomas that are infiltrating and destroy distal bronchioles. Cytology: Typical Langerhans cells may be detected in BAL fluids of patients suffering from active Langerhans cell histiocytosis. An increase in Langerhans cells greater than 4% of the total cell count is assumed to be reliably diagnostic for PLCH [12] . The total cell count in BAL fluids of patients with PLCH is increased due to proliferating Langerhans cells, and large numbers of histiocytes and macrophages. z z Sarcoidosis and other pulmonary disorders may be accompanied by a lower percentage of Langerhans cells in BAL fluids; a reliable diagnosis will not be possible in such cases . Therefore, a surgical lung biopsy is necessary in a high percentage of equivocal cases .

Lipoid pneumonia together with inflammatory and fibrotic changes in the lungs are caused by inhalation of various fatty substances or provoked by accumulation of endogenous lipid material in the lungs. Exogenous fatty material from outside the body includes, for example, inhaled nose drops with an oil base or accidental inhalation of cosmetic oil. Endogenous lipid pneumonia occurs when an airway is obstructed or following the fracture of a bone. 

This is a pneumonia induced by aspiration of foreign material into the lungs. The extraneous material includes fat, proteolytic and toxic substances, as well as plant cells and muscle fibers accidentally breathed into the respiratory system instead of being swallowed into the stomach. 

BAL in transplantation patients may be effective for the detection of pulmonary infectious pathogens and rare disorders complicating the course after lung transplantation, such as alveolar proteinosis [22] and obliterative bronchiolitis [47] . Whether a surveillance of BAL cell profiles has additive diagnostic value in routine lung transplant monitoring and in patients in whom rejection is suggested, is highly controversial and more often refused than accepted [47, 58, 66] .

Occasional atypias of epithelial cells in BAL specimens from lung (heart-lung) transplant recipients may demonstrate significant resemblance to carcinoma cells [41] .

Chapter 2  Respiratory Tract and Mediastinum Fig. 2.80A, B Pneumocystis jirovecii. Cytomorphologic appearance of the pathogen is demonstrated at low and high magnification from Pap-stained direct sediment smears. A Low magnification: Compact accumulation of pneumocysts presenting as a foamy mass with irregular outlines (arrow). The appearance is so characteristic that an accurate diagnosis can be established using conventional staining procedures. B High magnification shows sharply demarcated cysts, focal thickening of the cystic membranes, and grey-brown intracystic bodies (arrows).

Numerous intra-and extracellular yeast cells of varying size. Note the thick sharply demarcated capsule (arrow) (direct sediment smear, periodic-acid-Schiff stain, high magnification).

Accumulation of yeast cells in the cytoplasm of an activated multinucleated macrophage (direct sediment smear, Pap stain, high magnification).

A younger male patient suffering from AIDS presenting with cytomegalic inclusion disease in a BAL sample. Three affected epithelial cells are shown: two cells on the left exhibit the characteristic owl eye appearance; the cell at the right (arrow) seems to be in an earlier state of viral infestation (direct sediment smear, Pap stain, high magnification). A 56-year-old man presenting with multiple infiltrates in the right lung. Direct smears from a BAL sediment show numerous small and medium-sized compact three-dimensional clusters of epithelial cells with minor atypias. The papilliform cluster shown displays acini-like formations and monomorphic cell appearance Pap stain, (high magnification). Cytology: Cell changes are indeterminate between benign (hyperplastic type II pneumocytes) and malignant (bronchioloalveolar carcinoma). Comment: Compare cell features with those of a bronchioloalveolar carcinoma presented in Fig. 2 .85 for the distinct differences in nuclear texture and nuclear contour. Final diagnosis was Chlamydia pneumonia. Cytologic diagnosis: Adenocarcinoma. The overall cell pattern in comparison with the previous histomorphology is consistent with metastatic breast carcinoma. Comment: In cases with equivocal clinical history and absence of a preceding histologic/cytologic investigation, the differential diagnosis must also consider hyperplasia of type II histiocytes and bronchioloalveolar carcinoma. An appropriate immunopanel is helpful to solve the diagnostic problems.

BAL of a 38-year-old woman presenting with an uneventful history. Bronchoscopy revealed nonspecific inflammatory changes of the bronchial mucosa. Extremely cellular bronchoalveolar lavage fluids from the lung periphery showed a heterogeneous histiocytic population. Abnormal histiocytes exhibit multinucleation, nuclear cleaves and grooves, and vesicular chromatin (arrows). Positive immunostaining for S-100 and CD1 (immunocytochemistry not shown) classified the atypical cells as Langerhans cells accounting for 64% of the total number of histiocytic elements (direct sediment smear, MGG stain, high magnification). z z The encapsulated organ consists of two lobes and is divided into lobules by fibrous strands. The peripheral portion of the thymic lobes is the cortex, it appears darker than the central area, which is called the medulla. z z Parathyroid tissue is commonly found in the anterior mediastinum adjacent to the thymus gland or surrounded by thymic parenchyma.

The cortex is almost entirely composed of lymphocytes. The lymphoid population is best analyzed by flow cytometric analysis, which predominantly demonstrates T cells coexpressing CD4 and CD8 and staining positive for the early Tcell markers CD1a and TdT. A few small lymphoid follicles and rare plasma cells represent the B-cell lymphoid population. A few scattered cortical epithelial cells are difficult to distinguish from large histiocytes.

The medulla (Fig. 2 (Fig. 2.96) 

True thymic hyperplasia is characterized by an increase in the size and weight of the whole gland without changes in normal architecture and morphology for age. Common hyperplasia has to be separated from a true neoplastic disorder (thymoma). Massive benign enlargement of the thymus gland is rare. It has been described in children treated for malignancies and in conjunction with other pathological conditions [50] .

Follicular hyperplasia is characterized by the presence of germinal centers in the medullary area of the thymus gland. Follicular hyperplasia of lymphocytes of the B phenotype is often associated with myasthenia gravis and various autoimmune disorders [30] . Morphologic features of follicular hyperplasia are provided in Sect. 15.2.2, "Common Reactive Lymphadenopathy," p. 926.

z z A variety of information on diagnosis, differential diagnoses, and ancillary studies of the varied spindle cell lesions in FNAB samples are given in comprehensive publications by Geisinger [28] , and Slagel and coauthors [94] .

(Figs. 17.14-17.17)

The tumor group includes neurofibroma as well as benign and malignant schwannoma. The tumors are characterized by spindle-shaped cells; hence, the differential diagnosis includes a wide variety of benign and neoplastic conditions known to occur as primary or secondary tumors in the mediastinum. Paraganglia are clusters of neuroendocrine cells associated with the sympathetic and parasympathetic nervous system. They are located throughout the body at various sites. Tumors arising from these cells are referred to as paraganglioma, pheochromocytoma, carotid body tumor, and others. Adrenal medulla is one of the major locations of this neoplasm. Cytomorphology and differential diagnosis challenges of pheochromocytoma ( Fig. 12 

The tumors are derived from non-chromaffin cells and include neuroblastoma, ganglioneuroblastoma (Fig. 2.110 ), and ganglioneuroma ( Fig. 2.111 ). The three tumor entities together with differential diagnosis considerations are described in Sects. 12 

Thyroid and parathyroid tissue may be found in the superior/ anterior mediastinum as a primary ectopic lesion, a lesion extending from the cervical area into the mediastinal space, or a metastatic neoplasm. Goiters [88] , thyroid cysts, parathyroid cyst [75] , and parathyroid neoplasms [69] are among the most frequently diagnosed disorders on FNAB samples.

The thymus gland, mediastinal lymph nodes, and the mediastinal space can be affected by metastatic cancer. Metastases are the most common intrathoracic/extrapulmonary lesions diagnosed by FNAB. Tumor dissemination may occur by lymphogenic and hematogenic spreading, or by direct extension from adjacent structures and organs. Thymic and mediastinal metastasis is an indicator for generalized malignant disease. The most common source of mediastinal metastases is the lung, particularly small-cell carcinoma [28] . Breast, thyroid, head and neck tumors, malignant melanoma, and others are additional sources.

Trivial solid ectopic epithelial tissue should not be misinterpreted as metastasis in FNAB samples . CT-guided transthoracic FNAB of a mediastinal mass in an 11-year-old girl. The aspirated fluid originated from an inflammatory cystic lesion containing a few degenerating keratinized squamous cells (arrows) (direct sediment smear, Pap stain, low magnification). Cytology: A descriptive diagnosis was made. A more specific diagnosis was not possible. Tissue diagnosis (excision of the cystic mass): Cystic mature teratoma.

Transbronchial FNAB of a tumorous lesion located in the posterior mediastinum of a 66-yearold man. Fine-needle aspirate reveals proteinaceous cystic background, well preserved and degenerating columnar cells of the respiratory type, detached ciliary tufts (incompletely focused; arrows), and a few degenerating squamous cells (direct sediment smear, Pap stain, lower magnification). Tentative cytologic diagnosis: Bronchogenic cyst (confirmed by histology). Caution: reactive lymphoid cells should not lead to an erroneous diagnosis of malignant lymphoma.

Transthoracic FNAB of a tumor located in the anterior/superior mediastinum of a 48-year-old man. Low magnification shows the classical appearance of a cystic goiter: thyroidal parenchymatous tissue containing small follicles and a background with hemosiderophages (arrows) and colloid masses (direct smear, Pap stain). Fig. 2.95A , B Normal thymic gland Scraping from the medullary zone of the cut surface of a normal thymic gland (Pap stain). A A keratin pearl, so-called Hassall corpuscle is embedded in a lymphoid cell population (high magnification). B Sparsely dispersed and grouped (not in view) epithelial thymocytes; note single thymocytes exhibiting prominent nucleoli and a foamy cytoplasm of variable size (arrows) (lower magnification). Fig. 2.96A , B Thymic hyperplasia. Image-guided (CT) FNAB of a retrosternal tumorous lesion in a 35-year-old man. Direct smears were stained with the Papanicolaou method. Initial cytologic diagnosis in combination with clinical information was thymic hyperplasia. Tissue diagnosis (subsequent surgical biopsy): Thymus hyperplasia. A Numerous epithelial cells (arrows) intermingled with lymphocytes (high magnification). B Epithelial thymocytes are highlighted by positive immunostaining for pancytokeratin (Lu-5). Negative-staining lymphocytes are seen in the background (note their faint nuclear pseudopositivity) (Pap-prestained specimen).

Transthoracic FNAB of a voluminous cystic lesion (10 cm) in the anterior/superior mediastinum of a 5-year-old boy. Sediment preparations from the fluid revealed a sanguineous cystic background together with squamoid cells (arrows and asterisk), lymphocytes, and histiocytes (Pap stain, low magnification). Cytology suggested a thymic cyst. Histology: The cytologic diagnosis was confirmed by subsequent histologic examination of the excised tumor mass.

A 55-year-old man presented with a lesion in the anterior mediastinum; clinical and radiological findings suggested metastatic manifestation of a lung cancer. Image-guided transthoracic FNAB revealed a biphasic pattern comprising lymphocytes (showing deep-staining nuclei) and epithelial cells. The latter exhibit irregularly outlined nuclei, usually blurred nucleoli, and cytoplasmic bodies that are highly variable in size (direct smear, MGG stain, higher magnification). Epithelial thymocytes stained immunocytochemically positive for pancytokeratin Lu-5 (not shown). Cytologic diagnosis: Thymoma. Tissue diagnosis (tumor excision): Cortical thymoma. A 49-year-old man presented with a retrosternal tumor mass (anterior/superior mediastinum) associated with pleural and pericardial effusion. Image-guided transthoracic FNAB was performed. Direct smears were stained using the Papanicolaou procedure. Lower magnification reveals clusters composed of malignant spindle cells together with degenerating keratinized squamous cells in the background (right). Tumor cell nuclei showing dense and thinly dispersed chromatin may indicate thymic cell origin. Cytology and histology suggested squamous cell carcinoma of thymic origin, a secondary squamoid neoplasia to the mediastinum could not be excluded. Final diagnosis: Thymic squamous cell carcinoma. Fig. 2.102 and 2. 103 Thymic carcinoid. Two different patients underwent image-guided transthoracic fine needle aspiration biopsy of a thymic carcinoid. Cytomorphology and diagnostic challenge are discussed. Fig. 2.102 (case #1) Dissociated atypical cells exhibiting distinct variation in nuclear and cytoplasmic size (direct smear, MGG stain, high magnification). Cytology as a first-line diagnostic procedure established a diagnosis of epithelial thymoma, which turned out to be wrong. Absence of lymphocytes, pronounced variation of cell size, occasional plasmacytoid cell appearance (arrows), conspicuous granularity of the cytoplasm, frequent absence of nucleoli, and minor cellular clustering indicate endocrine origin of the neoplastic cells. Tissue diagnosis (extirpation of the tumor): Thymic carcinoid tumor. Fig. 2.103 (case #2) The current case of thymic carcinoid mimics the cytoarchitecture of an undifferentiated small-cell carcinoma (e.g., single-file cell arrangement and dense cell clustering; left). However, the tumor cell sheet (arrow) displays the characteristic features of a neuroendocrine tumors: eccentrically located nuclei, relatively bland nuclear texture, and granular cytoplasm (direct smear, Pap stain, lower magnification). Cytologic and subsequent histologic diagnosis: Thymic carcinoid. Fig. 2.104 Embryonal carcinoma. A 26-year-old man presenting with a voluminous mediastinal mass and nodular lesions in the liver. Transthoracic FNAB reveals the characteristic cumulative cell pattern of embryonal carcinoma: syncytial arrangement of pleomorphic neoplastic cells, abundant cytoplasms showing indistinct borders, variable N/C ratio, and varying nuclear size and shape. The chromatin tends to be coarse and clumped. Occasional prominent nucleoli. Multinucleation is frequent (direct smear, Pap stain, lower magnification). Immunocytochemistry revealed strong expression of pancytokeratin-Lu-5 (not shown). Cytologic diagnosis: Undifferentiated pleomorphic carcinoma, most likely embryonal carcinoma. Final diagnosis (extended pneumonectomy including tumor mass and imaging results): Undifferentiated embryonal carcinoma of the mediastinum infiltrating into the right lung, secondary liver tumors. Fig. 2.105 Hodgkin lymphoma: mixed cellularity. A 21-year-old man presented with a tumor mass in the anterior superior mediastinal space. Direct smears from a CT-guided transthoracic FNAB disclosed the classical cytologic pattern of mixed cellular variant Hodgkin lymphoma. Note the mixed cellular background (lymphocytes, neutrophils, eosinophils, histiocytes), Reed-Sternberg cells, and Hodgkin cells (MGG stain, lower magnification). Fig. 2.106 Hodgkin lymphoma: nodular sclerosis. A 26-year-old woman presented with a mediastinal-parasternal tumor mass with evidence of sternal bone and rib erosion. Image-guided transthoracic FNAB was performed. A direct smear of the paucicellular aspirate was prepared and Pap-stained. Microscopy revealed sporadic HRS cells (one Reed-Sternberg cell is depicted) together with scarce inflammatory background (low magnification). The smear with a paucity of cells may indicate a lesion comprising a high proportion of fibrosclerotic tissue. Tentative cytologic diagnosis: Malignant lesion comprising giant cells, most likely Hodgkin lymphoma. The FNA specimen is too paucicellular to provide a conclusive diagnosis. Tissue diagnosis: Hodgkin lymphoma, nodular sclerosis, G1. Transthoracic FNAB of a mediastinal tumor in a young woman. Direct smears revealed small and large malignant cells sometimes arranged in compact clusters (Pap stain, higher magnification). Cytology: Differential diagnostic considerations included high-grade malignant lymphoma, poorly differentiated carcinoma, and invasive thymoma (immunocytochemical analyses were not performed for technical reasons). Histologic diagnosis (surgical biopsy): Highly malignant sclerosing large-cell mediastinal lymphoma of the B-cell phenotype. Fig. 2.108A , B High-grade follicular non-Hodgkin lymphoma of the mediastinum. A transtracheal FNAB was performed in an elderly woman presenting with a mediastinal mass. Imaging and clinical data suggested metastatic lung carcinoma. The sanguineous but paucicellular aspirate was processed by the liquid-based ThinPrep method. Initial diagnosis by cytology: High-grade non-Hodgkin lymphoma. Tissue diagnosis: Follicular lymphoma, G2/G3a. A ThinPrep specimen contains blood and few large individual cells of atypical blast type (Pap stain, lower magnification). B CD45 immunostaining confirmed lymphoid origin of the large atypical cells (ThinPrep preparation, low magnification).

A 29-year-old man presented with a mediastinal tumor. Transbronchial aspirates were performed, direct smears were Pap-stained. Highly cellular smears revealed a uniform population of medium-sized tumor cells appearing solitary and in compact clusters (lower magnification). Cytology: The overall cell pattern caused diagnostic dilemma; a tentative cytologic diagnosis of epithelial thymoma was established. Tissue diagnosis including immunohistochemical investigations: mediastinal synovial sarcoma.

Two tumors of the sympathetic nervous system are demonstrated. Both lesions occurred in young patients' posterior mediastinum. Image-guided transthoracic FNABs were performed in order to reach an initial morphologic result. Direct smears were Pap-stained. A transtracheal aspirate from an enlarged mediastinal lymph node in a 74-year-old woman was processed using the cytospin technique. Cytologic and immunocytochemical diagnosis: Metastatic ovarian carcinoma, serous type (confirmed by postmortem examination). A Thin-layer specimens contained numerous cells of a poorly differentiated non-small-cell carcinoma (Pap stain, high magnification). B A panel of selected immunocytochemical markers established the aforementioned conclusive diagnosis: strong immunopositivity for CK7. C Positive immunoreaction for CK5/6. Negative immunoreaction for CK20 is not shown.

A 63-year-old man with a history of bladder cancer presented with enlarged mediastinal lymph nodes. The sanguineous transtracheal mediastinal aspirates were transferred to a hemolyzing fixative (Cytolyt) and subsequently processed using the cytospin technique. Tumor cells exhibiting polymorphic deep-staining nuclei and squamoid cytoplasm were strong indicators for transitional cell carcinoma (Pap stain, high magnification). Cytologic diagnosis: Metastatic transitional cell carcinoma. Neither surgical intervention nor histologic examinations were performed.

A 66-year-old man presented with a nonspecific lung disorder and enlarged mediastinal lymph nodes. The sanguineous transbronchial mediastinal aspirate was transferred to a hemolyzing fixative (Cytolyt) and subsequently processed by cytospin technique. Liquid-based cytology exhibits characteristic cell arrangement (short single-file rows, arrows), dense granular chromatin, and necrosis, indicating small-cell carcinoma (Pap stain, higher magnification). Simultaneous bronchial brushing yielded the same diagnosis. No tissue examination. 

Cytomegalic virus inclusion body in bronchial brushing material

Endoscopic ultrasound-guided fine needle aspiration in the evaluation of suspected lung cancer

Pulmonary tumorlet. A case report of a diagnostic pitfall in cytology

Changes in bronchial epithelium in relation to cigarette smoking 1955-1960 vs 1970-1977

Early detection of precancerous lesions in dysplasias of the lung by rapid DNA image cytometry

Preoperative cytodiagnosis of very small-sized peripheral-type primary lung cancer

Atypia status index of respiratory cells: a measurement for the detection and monitoring of neoplastic changes in squamous cell carcinogenesis

Diffuse alveolar damage. Morphologic features in bronchoalveolar lavage fluid

Exfoliative sputum cytology in pulmonary embolism

The usefulness of induced sputum in the diagnosis of Pneumocystis carinii pneumonia in patients with the acquired immunodeficiency syndrome

Improved procedure for the preparation of pulmonary cytology smears

The natural course of preneoplastic lesions in bronchial epithelium

Penicillium marneffei in bronchoalveolar lavage fluid

Sputum cell concentration by membrane filtration for cancer diagnosis: a preliminary report

Lung damage from cytotoxic drugs

Diagnostic dilemmas in pulmonary cytology

Morphologic changes in pulmonary oxygen toxicity

Sputum examination in the diagnosis of Pneumocystis carinii pneumonia in the acquired immunodeficiency syndrome

Induced sputum in patients with newly diagnosed sarcoidosis: comparison with bronchial wash and BAL

Stability of ferruginous bodies in human lung tissue following death, embalmment, and burial

Human pulmonary trichomonoses

Transesophageal ultrasound-guided fine needle aspiration imprroves mediastinal staging in patients with non-small cell lung cancer and normal mediastinum on computed tomography

Application of the Nedelkoff-Christopherson millipore method to sputum cytology

Cytologic distinction between bronchioloalveolar carcinoma and reactive/reparative respiratory epithelium: a cytomorphometric analysis

Viral infections of the respiratory tract . Cytopathologic and clinical analysis

Pneumocystis carinii: has the name really been changed?

An Online Quiz uncovers limitations of morphology in equivocal lung cytology

Computed tomography-guided fine needle aspiration of peripheral lung opacities. An initial diagnostic procedure?

Herpes simplex virus infection of the adult lower respiratory tract

The recognition of Pneumocystis carinii in routine Papanicolaou-stained smears

Morphometric markers for the evaluation of preneoplastic lesions in the lung. Diagnostic evaluation by high-resolution image analysis of atypical cells in sputum specimens

Reactive type II pneumocytes in bronchoalveolar lavage fluid from adult respiratory distress syndrome can be mistaken for cells of adenocarcinoma

Immunocytochemical characterization of isolated human type II pneumocytes

Fine needle aspiration cytology of lung lesions: a clinicopathological and cytopathological review of 150 cases with emphasis on the relation between the number of passes and the incidence of pneumothorax

Real-time endobronchial ultrasound guided transbronchial needle aspiration for sampling mediastinal lymph nodes

Multiple genetic and epigenetic biomarkers for lung cancer detection in cytologically negative sputum and a nested case-control study for risk assessment

Transbronchial fine needle aspiration cytological examination: a useful tool for diagnosing primary lung cancer

Cytomorphology of filariasis revisited. Expansion of the morphologic spectrum and coexistence with other lesions

Cytomegalic inclusion disease: Cytologic diagnosis from bronchial brushing material

Diagnostic respiratory cytopathology

False-positive sputum cytology in a case of pulmonary infarction

Diffuse alveolar damage -the role of oxygen, shock, and related factors. A review

Cytological evaluation of sputum in patients with bronchiectasis and the possibilities of erroneous diagnosis of cancer

Detection of lung cancer by automated sputum cytometry

Tumor-specific methylation in bronchial lavage for the early detection of non-small-cell lung cancer

Disseminated strongyloidiasis in AIDS and non-AIDS immunocompromised hosts: diagnosis by sputum and bronchoalveolar lavage

Endoscopic ultrasound-guided fine needle aspiration for diagnosis of recurrent nonsmall cell lung cancer

Genetic deletions in sputum as diagnostic markers for early detection of stage I non-small cell lung cancer

Errors and pitfalls in lung and pleural cytology

Diagnosis of lipid pneumonia by examination of sputum

Automated quantitative image cytometry of bronchial washings in suspected lung cancer: comparison with cytology, histology and clinical diagnosis

Cytologic diagnosis of laryngeal and hypopharyngeal squamous cell carcinoma in sputum

Solving the cytopreparation problem of mucoid specimens with a mucoliquefying agent (Mucolexx) and Nuclepore filters

Endoscopic ultrasound-guided fine-needle aspiration for non-small cell lung cancer staging: A systematic review and metaanalysis

Diagnosis of intraabdominal and mediastinal sarcoidosis with EUS-guided FNA

Cytopathological study of the sputum in cases of pulmonary cancer-tuberculosis association

Microfilariae in laryngeal and pharyngeal brushing smears from a case of carcinoma of the pharynx

Efficacy and pattern of use of sputum cytology as a diagnostic test

Cytological features of viral respiratory tract infections

Respiratory cytology: A review of nonneoplastic mimics of malignancy

Herpetic infection of the middle and lower respiratory tract

Cytomorphological grading and Feulgen DNA analysis of metaplastic and neoplastic bronchial cells

Cytologic findings indicating pulmonary tuberculosis. I. The diagnostic significance of epithelioid cells and Langhans giant cells found in sputum or bronchial secretions

A pitfall in the cytodiagnosis of sputum of asthmatics

Endoscopic ultrasound fine-needle aspiration in the staging of non-small-cell lung cancer

Induced sputum: diagnostic value in interstitial lung disease

Trichomonads in the respiratory tract. A case report and literature review

Cytologic diagnosis of complicated pulmonary unilocular cystic hydatosis. A study of 131 cases

Quantitative DNA determinations by image analysis. I. Application to human pulmonary cytology

Increase of sensitivity of sputum cytology using high-resolution image cytometry: field study results

Degenerative changes in ciliated cells exfoliating from the bronchial epithelium as a cytologic criterion in the diagnosis of diseases of the lung

The value of provoked expectoration in obtaining sputum samples for cytologic investigation. A prospective, consecutive and controlled investigation of 134 patients

The role of the Saccomanno technique in sputum cytopathologic diagnosis of lung cancer

The morphologic identification of Pneumocystis carinii

A comparative study: conventional preparation and ThinPrep 2000 in respiratory cytology

The histogenesis and development of pulmonary tumorlets

Pneumocystis and Trypanosoma cruzi: nomenclature and typifications

Endobronchial and endoscopic ultrasound-guided real-time fine-needle aspiration for mediastinal staging

Cytologic findings indicating pulmonary tuberculosis. II. The occurrence in sputum of epithelioid cells and multinucleated giant cells in pulmonary tuberculosis, chronic non-tuberculosis inflammatory lung disease and bronchogenic carcinoma. found in sputum or bronchial secretions

A direct comparison of natural and aerosol produced sputum collected from 776 asymptomatic men

Concentration of carcinoma or atypical cells in sputum

The sputum in bronchial asthma: Pathognomonic patterns

Multitarget fluorescence in situ hybridization elucidates equivocal lung cytology

Performance characteristics of different modalities for diagnosis of suspected lung cancer: summary of published evidence

Comparison of Papanicolaou's stain with the Gomori methenamine silver (GMS) stain for the cytodiagnosis of Pneumocystis carinii in bronchoalveolar lavage (BAL) fluid

Aspergillus-associated hypersensitivity respiratory disorders

Role of fine needle aspiration cytology in diagnosis of lung tumours -a study of 100 cases

Macrophages and polymorphonuclear neutrophils in lung defense and injury

Loss of FHIT function in lung cancer and preinvasive bronchial lesions

Mechanisms of macrophage accumulation in the lungs of as best-exposed subjects

Hyperplasia of type II pneumocytes in acute lung injury. Cytologic findings of sequential bronchoalveolar lavage

A review of pulmonary cytopathology in the acquired immunodeficiency syndrome

Protozoal infections in the acquired immunodeficiency syndrome

A comparative filter technique study and the relative efficiency of these sieves as applied in sputum cytology for pulmonary cancer cytodiagnosis

Sputum examination for early detection of lung cancer

A new technique to obtain sputum for cytologic study: External percussion and vibration of the chest wall

Pulmonary effects of cytotoxic agents other than bleomycin

Squamous metaplasia of the bronchus. A study of metaplastic changes occurring in epithelium of the major bronchi in cancerous and noncancerous cases

Oesophageal endoscopic ultrasound with fine-needle aspiration biopsy in the staging of nonsmall-cell lung carcinoma; results from 43 patients

The origin and turnover of alveolar macrophages in experimental pneumonia

The complete "medical" mediastinoscopy (EUS-FNA + EBUS-TBNA)

Progress report on study of respiratory spirals

Endobronchial ultrasound-guided fine-needle aspiration and liquid-based thinlayer cytology

Combined Pneumocystis carinii and cytomegalovirus infection

Alveolar type I and type II cells

Cytologic study of the sputum in cytomegalic inclusion disease

Pneumocystis carinii pneumonitis. The nature and diagnostic significance of the methenamine silverpositive "intracystic bodies

Chapter 4, lung. in: An Atlas of Radiation Histopathology. USERDA Technical Information Center

Preoperative staging of non-small cell lung cancer: transesophageal US-guided fine-needle aspiration biopsy of mediastinal lymph nodes

Histological technique for the examination of the cell content of sputum

Is endosonography-guided fine needle aspiration (EUS-FNA) for sarcoidosis as good as we think?

Predictive value of image cytometry for diagnosis of lung cancer in heavy smokers

Detection of DNA aneuploidy in exfoliated airway epithelia cells of sputum specimens by the automated image cytometry and its clinical value in the identification of lung cancer

Parasites in cytodiagnosis: a case report of Strongyloides stercoralis in Papanicolaou smears of gastric aspirate, with a review of the literature

Endobronchial ultrasoundguided transbronchial needle aspiration for staging of lung cancer

Flow cytometric evaluation of bronchoscopic washings and lavage fluid for DNA aneuploidy as an adjunct in the diagnosis of lung cancer and tumors metastatic to the lung

Distinction between bronchioloalveolar carcinoma and hyperplastic pulmonary proliferations: a cytologic and morphometric analysis

Giant cell carcinoma of the lung impact of diagnosis and review of cytological features

Molecular diagnostics of non-small cell lung cancer using mediastinal lymph nodes sampled by endoscopic ultrasound-guided needle aspiration

Metastatic pulmonary leiomyosarcoma: cytopathologic diagnosis on sputum examination

Exfoliative sputum cytology of cancers metastatic to the lung

Pulmonary tumorlet. A case report of a diagnostic pitfall in cytology

Significance of cytologic criteria in distinguishing small cell from non-small cell carcinoma of the lung

Exfoliative respiratory cytology in the diagnosis of leukemias and lymphomas in the lung

The value of cytology in the diagnostics of lung cancer

Thoracic endometriosis -2 case reports and review of the literature

The importance of epidermoid carcinomas in situ in the histogenesis of carcinoma of the lung

Sex hormone receptors in nonsmall-cell lung cancer in human beings

Neuroendocrine differentiation in lung cancer

Carcinomas of the lung with neuroendocrine differentiation

Lung cancer treated on the basis of cytologic findings: an analysis of 112 patients

The diagnosis of pulmonary small-cell anaplastic carcinoma by cytologic means: a 13-year experience

Intranuclear cytoplasmic inclusions in the differential diagnosis of papillary thyroid carcinoma and bronchioloalveolar carcinoma

Primary Hodgkin's disease of the lung

Immunostaining for thyroid transcription factor 1 and cytokeratin 20 aids the distinction of small cell carcinoma from Merkel cell carcinoma, but not pulmonary from extrapulmonary small cell carcinomas

Fine-needle aspiration cytologic diagnosis of lymphoepithelioma-like carcinoma of the lung. Report of two cases with immunohistochemical study

Expression of cytokeratin 5/6 in epithelial neoplasms: an immunocytochemical study of 509 cases

Diagnosis of adenoid cystic carcinoma of the lung by bronchial brushing: a case report

Lung Cancer: A status report

Pulmonary carcinosarcoma and carcinoma: report of a case studied by electron microscopy, with critical review of the literature

Report of a case with cytologic, histologic and electron microscopic study

Detection of estrogen receptor by immunohistrochemistry in pulmonary adenocarcinoma

Pulmonary preneoplasia

Exfoliative cytologic findings of primary pulmonary adenoid cystic carcinoma: a report of 2 cases with a review of the cytologic features

Bronchial oncocytoma

Small cell carcinoma versus other lung malignancies: diagnosis by fine-needle aspiration cytology

If it's not CK5/6 positive, TTF-1 negative it's not a squamous cell carcinoma of the lung

Preoperative diagnosis of clear cell "sugar" tumor of the lung by computed tomographyguided fine-needle biopsy and core-needle biopsy

Neuroendocrine tumors of the lung: recent developments in histopathology

Pulmonary Hodgkin'disease. Diagnosis by fine needle aspiration

The Mayo lung project for early detection and localization of bronchogenic carcinoma: A status report

Bronchial brushing cytology features of primary malignant fibrous histiocytoma of the lung. A case report

Fine-needle cytology of inflammatory myofibroblastic tumor of the lung

Fine-needle aspiration cytology of pleuropulmonary blastoma: case report and review of the literature

Sputum cytologic diag nosis of Hodgkin's disease involving the lung

Endometriosis of lung and pleura diagnosed by aspiration biopsy

Quantitation of Ki-67 expression in the differential diagnosis of reserve cell hyperplasia vs. small cell lung carcinoma

The spectrum of immunohistochemical staining of small-cell lung carcinoma in specimens from transbronchial and open-lung biopsies

Calcified (Psammoma) bodies in alveolar cell carcinoma of the lung

Value of sputum cytology in the differential diagnosis of alveolar cell carcinoma from bronchogenic adenocarcinoma

Respiratory Tract: Tumor-like lesions, Benign and malignant tumors 44. Hammar SP. Immunohistology of lung and pleural neoplasms

Fine needle aspiration biopsy and immunostaining findings in an aggressive inflammatory myofibroblastic tumor of the lung: a case report

Fine needle aspiration cytology of fibrous histiocytomas of the lung

Transthoracic fineneedle aspiration biopsy of pulmonary spindle cell and mesenchymal lesions: a study of 61 cases

A solitary bronchial papilloma with malignant changes

Granular cell tumor of the trachea in pregnancy: a case report and review of literature

Diagnosis of a case of pulmonary carcinosarcoma by detection of rhabdomyosarcoma cells in sputum

Expression of TTF-1 and cytokeratins in primary and secondary epithelial lung tumours: correlation with histological type and grade

Large cell neuroendocrine carcinoma of the lung: a histologic and immunohistochemical study of 22 cases

Fine-needle aspiration cytology of large cell neuroendocrine carcinoma of the lung. A cytohistologic correlation study of 11 cases

Adenomyomatous hamartoma of lung mimicking benign mucinous tumor in fine needle aspiration biopsy. A case report

Diagnostic respiratory cytopathology

Respiratory Tract. in:Comprehensive Cytopathology

Granular-cell tumours: an immunohistochemical study

Diagnostic findings of bronchial brush cytology for pulmonary large cell neuroendocrine carcinomas: comparison with poorly differentiated adenocarcinomas, squamous cell carcinomas, and small cell carcinomas

TTF-1 and p63 for distinguishing pulmonary small-cell carcinoma from poorly differentiated squamous cell carcinoma in previously pap-stained cytologic material

Cytologic features of peripheral squamous cell carcinoma of the lung

Sputum cytology of metastatic carcinoma of the lung

Pulmonary preinvasive neoplasia

Fine needle aspiration cytology of primary pulmonary paraganglioma. A case report

Lantuejoul Clear cell tumor of the lung: an immunohistochemical and ultrastructural study supporting a pericytic differentiation

Multiple nodular pulmonary amyloidosis. A case report and comparison with diffuse alveolar-septal pulmonary amyloidosis

Diagnosis of primary fibrosarcoma of the lung by fine-needle aspiration and core biopsy

Fine-needle aspiration biopsy of bronchioloalveolar carcinoma

Sputum cytology in the diagnosis of pulmonary non-Hodgkin's lymphoma

Transthoracic needle biopsy in the diagnosis of large-cell neuroendocrine carcinoma of the lung

Inflammatory pseudotumors of the lung: progression from organizing pneumonia to fibrous histiocytoma or to plasma cell granuloma in 32 cases

Chondrosarcoma of the trachea. A case report and literature review

Diagnosis of small cell carcinoma of the lung on fine needle aspiration samples

Cytology of endobronchial granular cell tumor

Pleomorphic carcinoma of the lung: Clinicopathologic characteristics of 70 cases

Sarcomatoid carcinoma of the lung: a clinicopathologic study of 37 cases

Cytopathologic and histologic features of biphasic pulmonary blastoma: a case report

Cytology of bronchial gland carcinoma

Cytopathology of pulmonary carcinoid tumors in sputum and bronchial brushings

Aspiration biopsy cytology of benign clear cell ("sugar") tumor of the lung

A review of cytologic findings in neuroendocrine carcinomas including carcinoid tumors with histologic correlation

The cytomorphology of pleuropulmonary blastoma

Thoracic endometriosis

Tracheo-bronchial cytology after laryngectomy for carcinoma of larynx. II. Benign atypias

Primary lung leiomyosarcoma detected by bronchoscopy cytology

Cytopathologic diagnosis of bronchioloalveolar carcinoma: does it correlate with the 1999 World Health Organization definition?

Value of ancillary studies in fine needle aspiration cytology of the lung

Epidemiology of lung cancer

Immunohistochemical markers of cancerogenesis in the lung

Chapter 2  Respiratory Tract and Mediastinum

Primary amyloid tumors of the lungs -six cases

Isolated pulmonary amyloidosis: case report and review of the literature

Fine needle aspiration cytology of clear cell "sugar" tumor (PEComa) of the lung: report of a case

A comparative study: conventional preparation and ThinPrep 2000 in respiratory cytology

intrapulmonary teratoma: an exceptional disease

The histogenesis and development of pulmonary tumorlets

Distinguishing carcinoid tumor from small cell carcinoma of the lung: correlating cytological features and performance in the College of American Pathologists Non-Gynecologic Cytology Program

Distinguishing small cell carcinoma from non-small cell carcinoma of the lung: correlating cytologic features and performance in the College of American Pathologists Non-Gynecologic Cytology Program

Cytologic differential diagnosis of bronchiolo-alveolar carcinoma and bronchogenic adenocarcinoma

Cytology of the solitary papilloma of the bronchus

Intranuclear inclusions in fine needle aspirates of bronchial low grade mucoepidermoid carcinoma with clear cell change: a report of two cases

Pulmonary carcinomas with pleomorphic, sarcomatoid, or sarcomatous elements: a clinicopathologic and immunohistochemical study of 75 cases

Cytologic description of squamous cell papilloma of the respiratory tract

Cytologic diagnosis of pulmonary adenocarcinoma with micropapillary pattern (MPP)

Cancer of the lung: the cytology of sputum prior to the development of carcinoma

Bronchioloalveolar carcinoma: diagnostic pitfalls and immunocytochemical contribution

Lung cancer at a university hospital: epidemiological and histological characteristics of a recent and a historical series

High cellular atypia in a pulmonary tumorlet

Equivocal cytology in lung cancer diagnosis:improvement of diagnostic accuracy using adjuvant multicolor FISH, DNA-image cytometry, and quantitative promoter hypermethylation analysis

Cytology of primary pulmonary mucoepidermoid and adenoid cystic carcinoma. A report of four cases

Fine needle aspiration cytology of bronchioloalveolar-cell carcinoma of the lung

Adenocarcinoma of the lung. Cytologic correlation with histologic types

Alveolar-cell carcinoma: a problem in sputum cytodiagnosis

Reed-Sternberg cells in sputum from a patient with Hodgkin's disease. A case report

The value of immunohistochemical identification of neuroendocrine differentiation in non small cell lung carcinoma

Cytology of fine-needle aspiration of inflammatory myofibroblastic tumor

Expression of thyroid transcription factor-1 in the spectrum of neuroendocrine cell lung proliferations with special interest in carcinoids

Expression of estrogen and progesterone receptors in non-small-cell lung cancer: immunohistochemical study

Primary pulmonary amyloidosis with multiple nodules

Cytologic diagnosis of bronchioloalveolar carcinoma by fine-needle aspiration biopsy

Cytomorphology of granular-cell tumor of the bronchus. A case report

Fine needle aspiration cytology of inflammatory pseudotumor of the lung (plasma cell granuloma)

World Health Organization Classification of Tumours. Pathology and Genetics of Tumours of the Lung, Pleura, Thymus and Heart

International association for the study of lung cancer/american thoracic society/european respiratory society international multidisciplinary classification of lung adenocarcinoma

Pathological Diagnosis and Classification of Lung Cancer in Small Biopsies and Cytology: Strategic Management of Tissue for Molecular Testing

Solitary condylomatous papilloma of the bronchus

Pulmonary spindle cell lesions: correlation of aspiration cytopathology and histopathology

Cytologic and histologic findings in a case of tracheobronchial papillomatosis

Large-cell neuroendocrine carcinoma of the lung: proposed criteria for cytologic diagnosis

Fine needle aspiration biopsy of pulmonary hamartomas. Radiologic, cytologic and immunocytochemical study of 15 cases

Primary cytodiagnosis of synchronous small-cell cancer and squamous-cell carcinoma of the respiratory tract

Lung cancer preneoplasia

Diagnosis of pulmonary hamartoma by fine needle biopsy

World Health Organization. Histological typing of lung tumors

Report of a case diagnosed by fine needle aspiration cytology

Diagnosis of high-grade pulmonary neuroendocrine carcinoma by fine-needle aspiration biopsy: nonsmall-cell or small-cell type?

Endometriosis within the thorax: metaplasia, implantation, or metastasis?

Cytomorphology of the variants of small-cell carcinoma of the lung

Cytologic examination of bronchoalveolar lavage fluid from immunosuppressed patients

Asbestosis mortality in the United States: Facts and predictions

Technical aspects of bronchoalveolar lavage: recommendations for a standard procedure

Amiodarone pulmonary toxicity: Cytopathology, Ultrastructure, and Immunocytochemistry

Pneumothorax secondary to pulmonary histiocytosis X

Bronchoalveolar lavage cytology in pulmonary alveolar proteinosis

Bronchoalveolar lavage in occupational lung diseases

Bronchoalveolar lavage in interstitial lung disease

Pulmonary alveolar proteinosis: a new autoimmune disease

Atlas of Bronchoalveolar Lavage

Bronchoalveoläre Lavage bei diffusen malignen Lungenveränderungen

Bronchoalveolar lavage in other interstitial lung diseases

Bronchiolitis obliterans organizing pneumonia (BOOP): The cytological and immunocytological profile of bronchoalveolar lavage

Transport of bronchoalveolar lavage cells in appropriate medium for 24 hours does not affect cell differentials and lymphocyte subsets (abstract)

Eosinophilic pneumonias

Broncho-alveolar lavage cell-lymphocyte interactions in normal non smokers and smokers

BAL in the diagnosis of smoking-related interstitial lung disease: review of literature and analysis of our experience

Bronchoalveolar lavage in sarcoidosis

Laboratory diagnosis of cytomegalovirus infection and disease in immunocompromised patients

Accuracy of a routine realtime PCR assay for the diagnosis of Pneumocystis jirovecii pneumonia

From the archives of the AFIP: pulmonary alveolar proteinosis

Cytopathology of pulmonary alveolar proteinosis complicating lung transplantation

Churg-Strauss syndrome: 2005-2008 update

Diagnostic value of hemosiderincontaining macrophages in bronchoalveolar lavage

Mast cells, atypical lymphocytes and neutrophils in bronchoalveolar lavage in extrinsic allergic alveolitis

Extrinsic allergic alveolitis

The CD4/CD8 ratio in BAL fluid is highly variable in sarcoidosis

Natural and synthetic mineral fibers affecting man

Clinical guidelines and indications for bronchoalveolar lavage (BAL): Report of the European Society of Pneumology Task Group on BAL

Clinical guidelines and indications for bronchoalveolar lavage (BAL): Report of the European Society of Pneumology Task Group on BAL

Bronchoalveoläre Lavage be pulmonaler Beteiligung systemischer Erkrankungen

Chronic pulmonary sarcoidosis: Relationship between lung lavage cell counts, chest radiograph, and results of standard lung function tests

Early effects of short-time cigarette smoking on the human lung: a study of bronchoalveolar lavage fluids

Smoker's lung transplanted to a nonsmoker. Long-term detection of smoker's macrophages

Pulmonary alveolar proteinosis: a spectrum of cytologic, histochemical, and ultrastructural findings in bronchoalveolar lavage fluid

Bronchoalveolar lavage as a diagnostic tool

Value of bronchoalveolar lavage in the diagnosis of lung disease

Significance of the presence of mastocytes in bronchoalveolar lavage in the diagnostic evaluation of diffuse interstitial lung disease

Diagnosis of parenchymal Hodgkin's disease using bronchoalveolar lavage

Utility of reflex Gomori methenamine silver staining for Pneumocystis jirovecii on bronchoalveolar lavage cytologic specimens: a review

Epithelial cell atypia in bronchoalveolar lavage specimens from lung transplant recipients

Role of inflammation in the lung disease of systemic sclerosis: Comparison with idiopathic pulmonary fibrosis

Analysis of six cases in comparison with other interstitial lung diseases

Clinical utility of bronchoalveolar lavage in immunocompromised hosts

Bronchoalveolar lavage in malignancy

Bronchoalveolar lavage in the diagnosis of disseminated lung tumors

Chapter 2  Respiratory Tract and Mediastinum

Clinical utility of bronchoalveolar lavage cell phenotype analyses in the postoperative monitoring of lung transplant recipients

Alveolitis of pulmonary asbestosis

Bronchoalveolar lavage as a research tool

Is chronic beryllium disease sarcoidosis of known etiology?

Bronchoalveolar lavage in fibrotic idiopathic interstitial pneumonias

Mast cells in bronchoalveolar lavage fluid of patients with interstitial lung disease

Bronchoalveolar lavage cell profiles in Wegener's granulomatosis

BAL findings in a patient with pulmonary alveolar proteinosis successfully treated with GM-CSF

Pulmonary alveolar proteinosis. A report of two cases with diagnostic features in bronchoalveolar lavage specimens

Pathologic quiz case: Recurrent spontaneous pneumothorax in an industrial worker

Adult pulmonary Langerhans cell histiocytosis

Bronchoalveolar lavage in lung transplantation. State of the art

Bronchoalveoläre Lavage

Nagarjun Rao R. Pathologic Quiz Case. Pulmonary infiltrates with characteristic light and electron microscopic features

Eosinophilic pneumonia associated with heroin inhalation: a case report

The value of serial bronchoalveolar lavages in assessing the clinical progress of patients with cryptogenic fibrosing alveolitis

Prognostic value of neutrophils and NK cells in bronchoalveolar lavage of sarcoidosis

BAL findings in idiopathic nonspecific interstitial pneumonia and usual interstitial pneumonia

Bronchoalveolar lavage cell and lymphocyte phenotype profiles in healthy asbestos-exposed shipyard workers

Bronchoalveolar lavage cell populations in the diagnosis of sarcoidosis

Pulmonary Langerhans cell histiocytosis (Histiocytosis X) on bronchoalveolar lavage. A report of 2 cases

Chapter 2  Respiratory Tract and Mediastinum z { Fine-needle aspiration usually contains cells of ectodermal origin (squamous cells, sebaceous cells, squamous epithelium detritus). Calcification and a granulomatous response to keratin including foreign body giant cells are common

Fine-needle aspiration biopsy of mediastinal masses: evaluation of 136 experiences

Cytodiagnosis of yolk sac tumor. Indian

Fine-needle aspiration biopsy of seminoma and dysgerminoma: cytologic, histologic, and electron microscopic correlations

Cytopathologic features and differential diagnosis on fine needle aspiration

Endobronchial ultrasound-guided (EBUS) transbronchial fine needle aspiration (FNA): The University of Minnesota initial experience

Diagnostic accuracy of image-guided percutaneous fine needle aspiration biopsy of the mediastinum

Cytomorphologic features characteristic of tumor stages of thymomas

Malignant melanoma of mediastinum misdiagnosed as a spindle cell thymoma in a fine needle aspirate: a case report

Tumors of the thymus and thymic region: II Clinicopathological studies on Hodgkin's disease of the thymus

Endosonographic guided fine needle aspiration (EUS-FNA) in mediastinal and abdominal lesions: accuracy and patients tolerance

Cytologic versus histologic evaluation of needle biopsy of the lung, hilum and mediastinum: sensitivity, specificity and typing accuracy

Localized mediastinal lymph node hyperplasia resembling thymoma

Endoscopic ultrasound-guided fine needle aspiration in the diagnosis of mediastinal masses of unknown origin

Cytology of thymomas: emphasis on morphology and correlation with histologic subtypes

Fine-needle aspiration biopsy of nonteratomatous germ cell tumors of the mediastinum

Lymphangioma of the posterior mediastinum in an adult: diagnosis via cytopathologist-assisted fine-needle aspiration biopsy with cell block

Germ cell tumors of the mediastinum

Thymic carcinomas, but not thymomas and carcinomas of other sites, show CD5 immunoreactivity

Endoscopic ultrasoundguided fine-needle aspiration in the diagnosis of foregut duplication cysts: the value of demonstrating detached ciliary tufts in cyst fluid

Utility of immediate evaluation of endoscopic ultrasound-guided transesophageal fine needle aspiration of mediastinal lymph nodes

Transesophageal ultrasound-guided fine needle aspiration improves mediastinal staging in patients with non-small cell lung cancer and normal mediastinum on computed tomography

Malignant thymic neoplasms: diagnosis by fine-needle aspiration biopsy with histologic, immunocytochemical, and ultrastructural confirmation

Hodgkin's disease masquerading as sclerosing mediastinitis

Idiopathic fibroinflammatory (fibrosing/sclerosing) lesions of the mediastinum: a study of 30 cases with emphasis on morphologic heterogeneity

Thymoma mimicking lymphoblastic lymphoma: a pitfall in fine-needle aspiration biopsy interpretation

Flow cytometric study of lymphocytes associated with thymoma and other thymic tumors

Differential diagnostic considerations and potential pitfalls in fine-needle aspiration biopsies of the mediastinum

Diagnosis of metastatic thymoma using flow cytometry

Utility of fine needle aspiration cytology in mediastinal lesions. A clinicopathologic study of 161 cases from a single institution

An electron microscopic study of the human thymus: Normal appearances and findings in myasthenia gravis and systemic lupus erythematosus

Ultrasound guided fine needle aspiration biopsy in mediastinal tuberculosis

Diagnosis of foregut and tailgut cysts by endosonographically guided fine-needle aspiration

Report of five cases and review of the literature

Anterior mediastinal masses: Utility of transthoracic needle biopsy

Real-time endobronchial ultrasound guided transbronchial needle aspiration for sampling mediastinal lymph nodes

Fine-needle aspiration of a primary mediastinal large B-cell lymphoma: a case report with cytologic, histologic, and flow cytometric considerations

Fine-needle aspiration cytology of mediastinal non-Hodgkin's nonlymphoblastic lymphoma

Correlating genetic aberrations with World Health Organization-defined histology and stage across the spectrum of thymomas

Thymoma: update for the new millennium

The angiofollicular lymph node hyperplasia Castleman -casuistic and review of the literature

Analysis of cytological specimens from mediastinal lesions obtained by endoscopic ultrasoundguided fine-needle aspiration

Oesophageal endoscopic ultrasound with fine needle aspiration improves and simplifies the staging of lung cancer

Mediastinal cysts: diagnosis by CT and needle aspiration

Fine needle aspiration diagnosis of bronchogenic cysts

Aspiration cytology of mediastinal seminoma: report of a case with emphasis on the diagnostic role of aspiration cytology, cell block and immunocytochemistry

Malignant thymoma: current status and future directions

A spindle cell variant of thymic carcinoid. A clinical, histologic and fine structural study with emphasis on its distinction from spindle cell thymoma

Thymoma: A clinicopathologic review

Cytomorphology of hyalinevascular Castleman's disease: a diagnostic challenge

Surgical Pathology of the Mediastinum

A case of malignant thymoma mimicking thyroid carcinoma: a pitfall in fine-needle aspiration

Fine-needle aspiration findings in Castleman's disease

Endoscopic ultrasound-guided fine-needle aspiration for non-small cell lung cancer staging: A systematic review and metaanalysis

Thymoma presenting as a palpable thyroid nodule: a pitfall in fine needle aspiration (FNA) of the neck

Sclerosing mediastinitis: a report on 18 cases

Thymic carcinoma: current concepts and histologic features

Primary germ cell tumors of the mediastinum: III. Yolk sac tumor, embryonal carcinoma, choriocarcinoma, and combined nonteratomatous germ cell tumors of the mediastinum -a clinicopathologic and immunohistochemical study of 64 cases

Fine needle aspiration cytology of primary mediastinal germ cell tumors

Fine needle aspiration cytology in mediastinal myxoid liposarcoma: a case report

Primary intrapulmonary thymoma: a systematic review

Immunohistochemical KIT (CD117) expression in thymic epithelial tumors

Flow cytometric analysis of lymphoid cells in thymic epithelial neoplasms

Castleman's disease: three case reports and a review of the literature

Mediastinal germ cell tumors: Clinical features and biological correlates

Report of a case with diagnosis by fine needle aspiration biopsy

Diagnostic utility of thymic epithelial markers CD205 (DEC205) and Foxn1 in thymic epithelial neoplasms

Thymoma mimicking thyroid papillary carcinoma: another pitfall in fine-needle aspiration

Endoscopic ultrasound fine-needle aspiration in the staging of non-small-cell lung cancer

A case of mediastinal parathyroid adenoma diagnosed by transtracheal needle aspiration

Three-color flow cytometric study on lymphocytes derived from thymic diseases

Clinical and pathological aspects of thymic epithelial tumors

Thyroid transcription factor-distinguishes metastatic pulmonary from well-differentiated neuroendocrine tumors of other sites

Myxoid liposarcoma of the breast in a 25-year-old female as a diagnostic pitfall in fine needle aspiration cytology: report of a rare case

Mediastinum thymoma diagnosed by FNA and ThinPrep technique: a case report

Parathyroid cyst: Report of a case in the mediastinum

Fine needle aspiration for diagnosing a thymoma producing CA-125. A case report

Immunohistochemical markers in the differentiation of thymic and pulmonary neoplasms

Diagnosis of cervical thymoma by fine needle aspiration biopsy with flow cytometry. A case report

Fine-needle aspiration cytology of thymic basaloid carcinoma: case studies and review of the literature

Fine-needle aspiration biopsy of the mediastinum. A multi-institutional analysis

CT-guided percutaneous transthoracic biopsy in the diagnosis of mediastinal masses: evaluation of 73 procedures

Acute mediastinitis: clinical features and review of a case load

Distinguishing carcinoid tumor of the mediastinum from thymoma. Correlating cytologic features and performance in the College of American Pathologists Interlaboratory Comparison Program in Nongynecologic Cytopathology

Epithelial cytologic atypia in fine needle aspirate of an invasive thymoma. A case report

Endobronchial and endoscopic ultrasound-guided real-time fine-needle aspiration for mediastinal staging

Chapter 2  Respiratory Tract and Mediastinum

Diagnosis of thymolipoma with fine needle aspiration biopsy

Benign developmental cysts of the mediastinum

Mediastinal goiters: The need for an aggressive approach

Primary mediastinal large B-cell lymphoma

Granulomatous and fib rous mediastinitis: A review and analysis of 180 cases

Diagnosis and treatment of a bronchogenic cyst using transbronchial needle aspiration

Diagnostic accuracy and role of immediate interpretation of fine-needle aspiration biopsy specimens from various sites

Fine-needle aspiration cytology of primary large-cell lymphoma of the mediastinum: cytomorphologic findings with potential pitfalls in diagnosis

Spindle cell lesions of the mediastinum: Diagnosis by fine-needle aspiration biopsy

Mediastinal lymphoma

Primary large-cell lymphomas of the mediastinum

Tungsagunwattana S. Fine needle aspiration cytology of thymoma

Cytopathology of thymoma

Immunoreactivity of new CD5 antibody with normal epithelium and malignant tumors including thymic carcinoma

Cytologic demonstration of "dysplastic" follicular dendritic cells in a case of hyaline-vascular Castleman's disease

A clinicopathologic study of 12 neuroendocrine tumors arising in the thymus

World Health Organization Classification of Tumours. Pathology and Genetics of Tumours of the Lung, Pleura, Thymus and Heart

Oesophageal endoscopic ultrasound with fine-needle aspiration biopsy in the staging of non-small-cell lung carcinoma; results from 43 patients

Cytomorphologic spectrum in paraganglioma

Invasive cervical thymoma masquerading as a solitary thyroid nodule: Report of a case studied by fine needle aspiration

The complete "medical" mediastinoscopy (EUS-FNA + EBUS-TBNA)

Fine needle aspiration in the diagnosis of thymic epithelial neoplasms

Endobronchial ultrasound-guided fine-needle aspiration and liquid-based thinlayer cytology

Fine needle aspiration cytology of thymic carcinoid tumor

Ectopic pancreas in mediastinum: report of 2 cases and review of the literature

Preoperative staging of non-small cell lung cancer: transesophageal US-guided fine-needle aspiration biopsy of mediastinal lymph nodes

Primary germ cell tumors of the mediastinum: 10 years of experience in a tertiary teaching hospital

Endobronchial ultrasoundguided transbronchial needle aspiration for staging of lung cancer

Flow-cytometric diagnosis of thymoma using needle biopsy specimens

Thymic epithelial cells as a diagnostic pitfall in the fine-needle aspiration diagnosis of primary mediastinal lymphoma

z z An activated lymphocytic population in EAA should not lead to a misdiagnosis of malignant lymphoma. z z In the course of EAA, the CD4 T-helper cell fraction and subsequently the CD4/CD8 ratio may increase, a finding that may be misinterpreted as sarcoidosis.z z Granulomatous reaction in chronic stages of EAA can also be encountered in BAL fluids, i.e., granulomatosis is not a specific sign of sarcoidosis. Evaluation of the lymphocyte surface antigen phenotypes provides a correct diagnosis. Synonym: Bronchiolitis obliterans with organizing pneumonia (BOOP) Cryptogenic organizing pneumonia (COP) is an inflammatory lung disease with distinct clinical, radiological, and histopathological features. The latter consist of intraalveolar buds of granulation tissue, rich in active fibroblasts and myofibroblasts. COP may be triggered by infectious agents as well as by drugs and toxic fumes. The disease usually begins between the ages of 40 and 60 and affects men and women equally.

Additional Comments z z The lymphocyte rate is relatively high and the CD4/CD8 ratio is reduced to a degree barely observed in BAL fluids of other interstitial lung disorders. z z The proportion of CD57 + NK cells is not increased. z z Plasma cells are a common feature in both COP and EAA. z z Mast cells can be significantly increased in individual cases of COP [52] .

z z COP differs from EAA in a normal CD57 + NK cell number and in a lower CD4/CD8 ratio. z z Low lymphocyte percentage of less than 20% makes the diagnosis of COP quite unlikely; however, idiopathic pulmonary fibrosis should primarily be taken into consideration.z z Chronic eosinophilic pneumonia exhibits a high percentage of eosinophils exceeding 20% of the total cell count, a rate that has rarely been encountered in COP. Compared to BAL results in patients with COP, most patients with eosinophilic pneumonia show a higher eosinophil percentage than lymphocyte percentage [13] .

Drug-induced lung damage induces a wide range of BAL cellular changes comprising lymphocytic, neutrophilic, or eosinophilic predominance. Still, lymphocytosis associated with a low CD4/CD8 ratio is most commonly seen. Numerous drugs with their cytologic patterns observed in BAL fluids have been presented in table form by Costabel [10] and Tötsch and coauthors [59] .

z z Alveolar hemorrhage syndrome may sometimes be linked with drug-related lung damage.z z A characteristic but not specific cell feature is observed in amiodarone lung (Fig. 2.71 ): macrophages displaying extremely pronounced cytoplasmic vacuolization. Ultrastructurally, the cytoplasmic deposits occur in lamellar arrangement similar to surfactant lamellar bodies [60] .The characteristic macrophages may also be found in BALs of patients taking amiodarone but lacking pneumopathy [4] . z z Hyperplastic type II pneumocytes seem to occur mainly in combination with interstitial fibrosis [4] .

z z Differential cytology may sometimes mimic the cell constellation seen in EAA or COP. z z Amiodarone-induced foamy vacuolization in the cytoplasm of macrophages is not a specific feature but vacuolization of macrophages in EAA and COP is usually less pronounced.z Reactive cell changes induced by chemotherapy (and irradiation) can reliably be recognized by experienced microscopists, even though substantial degenerative changes of atypical cells may raise differential diagnostic problems. A drug-induced hyperplastic process of the epithelium of the bronchi, terminal bronchioli, and alveoli (type II pneumocytes) may simulate adenocarcinoma, both on exfoliated single cells and cell clusters ( Fig. 2.84 ). The varied morphologic characteristics, differential diagnostic considerations, cautions, and potential auxiliary analyses regarding hyperplastic cell alterations are discussed in Sect. 2.1.4, "Abnormal and Atypical Epithelial Cells," p. 112 . z z Activated macrophages may closely mimic proliferating type II pneumocytes. Immunocytochemistry can separate the two histogenetically different cell types: macrophages are positive for lysozyme (and other histiocytic markers) and negative for EMA, CEA, and cytokeratins [4] . [10] (Tab. 2.3.6)

Idiopathic interstitial pneumonia (IIP) is an alveolar disorder of unknown etiology. A primary alveolitis is followed by chronic inflammation and progressive fibrosis of the pulmonary alveolar walls with steady progressive dyspnea as a striking clinical symptom. The disease usually affects males and females aged between 40 and 70 years.

z z An increased number of neutrophils is observed in up to 90% of all cases with idiopathic pulmonary fibrosis. Many of the cases (up to 60%) show a parallel increase in eosinophilic granulocytes [43] .z z Lymphocytosis may be observed in up to 20% of all cases.z z Differential cytology in BAL can be helpful in assessing the degree of activity of the disease and may act as prognostic indicator. In this respect, an increased percentage of lymphocytes is presumed to be an indicator of a better prognosis [51, 62] .

z z A normal cell distribution in BAL makes idiopathic pulmonary fibrosis an improbable diagnosis; in contrast, any abnormal BAL cell pattern caused by IIP has a large variety of differential diagnoses. z z Several reports in the literature deal with the subject of discrimination between different types of interstitial pneumonia using cell counts in BAL: the results have not been consistent [17, 51, 64] .Chapter 2  Respiratory Tract and Mediastinum z z Bronchial asthma is commonly found in patients with Churg-Strauss syndrome, chronic eosinophilic pneumonia, and in most of the interstitial lung disorders caused by specific respiratory allergens. BAL cytology reveals mild to moderate eosinophilia and an occasional increase in neutrophils and mast cells. In general clinical practice, the cytologic examination of BAL fluids in patients with bronchial asthma is of little significance. Lung hemosiderosis may be caused by unknown factors (idiopathic hemosiderosis). However, many underlying disorders exist for hemorrhage syndromes of the alveolar space such as autoimmune disease, vasculitis, cardiovascular diseases, drugs, hematological diseases, or post-transplantation conditions. The most common causes for alveolar hemorrhage have been compiled and tabulated by Costabel [10] .

z z The characteristic hemosiderin-relevant greenish or green-brown color of the cytoplasm of macrophages is not always clearly apparent on routine staining procedures (Papanicolaou and May-Grünwald-Giemsa). Therefore, iron staining (e.g., the Prussian-blue method) should always be performed in morphologically doubtful cases and in all cases with clinical doubt. z z Different scoring systems have been applied to create hemosiderin scores, but differential diagnostic conclusions on the basis of a semiquantitative assessment of the cytoplasmic hemosiderin deposits are limited. Grebski and coauthors found the highest hemosiderin scores in patients suffering from immunomediated diseases known to cause alveolar hemorrhage, and in selected groups of patient who had undergone heart transplantation [24] .z z Chronic hemorrhage syndrome may show a cytologic appearance, as observed in idiopathic pulmonary fibrosis comprising increases in neutrophils and eosinophils. z z Certain occupational categories such as metal workers or welders are exposed to iron uptake from exogenous sources. Iron-laden macrophages are usually larger with more polymorphic cytoplasm and dust inclusions; ironcontaining particles are often bizarre and irregular in shape and size. z z In general, the overall pattern of severe endogenous and exogenous siderosis is not very different: up to 100% of the macrophages exhibit strong positivity to iron stains.

z z Bronchoalveolar lavage in occupational lung diseases have been broadly covered by Costabel [10] and recently by Cordeiro and coauthors [7] . z z Pneumoconiosis is an occupational lung disease caused by inhalation of inorganic dust particles. The disease usually runs a chronic course ending in generalized interstitial lung disease. Dust particles may be permanently but not completely removed from the alveolar space by uptake in the interstitium (elimination through the lymphatic system) and by proximal transport of the mucus stream. Dust particles may be found trapped in macrophages decades after exposure to dust. z z More information on alveolar macrophages and their morphology is provided in Sect. 2.1.3.2.1 "Pulmonary Alveolar Macrophages," p. 111. positive particles. The particles are coarser compared to those packed in macrophages due to alveolar bleeding. But in general, the overall pattern of severe endogenous and exogenous siderosis is not very different: up to 100% of the macrophages exhibit strong positivity to iron stains.Chronic Berylliosis (Tab. 2.3.9) This is a chronic lung disease caused by exposure to beryllium and its compounds. In 1-3% of workers with single or prolonged exposure by inhalation, the lungs become hypersensitive to beryllium and develop generalized inflammatory nodules. These granulomas are hard to distinguish from granulomas in tuberculosis and sarcoidosis. The similarities and disparities between sarcoidosis and chronic berylliosis have been reviewed by Rossman and Kreider [50] .

Hard metal lung: Specific elements such as cobalt, titanium, nickel, and others can be traced, for example through radiochemical analysis. Antimony lung: Typical crystalline elements are found as cytoplasmic inclusions in BAL macrophages and as background material in BAL sediments. [21] (Figs. 2.78 and 2.79) (Tab. 2.3.10)) z z More than 15 years ago, idiopathic alveolar proteinosis (AP) was recognized as an autoimmune disease caused by neutralizing anti-granulocyte-macrophage colony-stimulating autoantibodies (anti-GM-CSF) [9, 54] . z z Secondary AP can occur in patients with pulmonary infections, malignant diseases, particular hematologic malignancies, particular occupational exposures, and as a reaction to drugs. z z Impaired pulmonary surfactant homeostasis is regarded as an additional mechanism in the pathogenesis of AP. There is a strong association between incidence of alveolar proteinosis and tobacco use.

z z BAL specimens with the characteristic macroscopic, cytologic and ultrastructural features provide a reliable diagnosis of alveolar proteinosis [6, 35, 55] .

z z The homogeneous granular material is typically PAS-positive and diastase-resistant ( Fig. 2.78 ). mic in macrophages. Surfactant is a complex substance containing phospholipids and a number of proteins. The substance is produced by the type II pneumocytes and lines the alveoli and smallest bronchioles. Surfactant reduces surface tension throughout the lung and stabilizes the alveoli. z z Treatment of alveolar proteinosis by lavage eliminates the majority of lipoproteins. The morphologic changes of BAL fluid in a patient with alveolar proteinosis successfully treated with GM-CSF has been reported by Schoch and coauthors [54] .

z z Lung disorders, other than alveolar proteinosis, which include a dirty background in cytologic preparations of BAL fluid should be diagnostically approached with caution. Such lesions include pulmonary edema, radiation pneumonitis, Pneumocystis jiroveci pneumonia, acute respiratory distress syndrome, among others [35] . z z Persisting lymphocytosis and increased CD4/CD8 ratio, notably observed after successful treatment of alveolar proteinosis, may mimic other pulmonary disorders such as sarcoidosis, extrinsic allergic alveolitis, nonspecific interstitial pneumonia, idiopathic pulmonary fibrosis, and pneumoconiosis [54] . z z AP lavage specimens containing the following elements may mimic lipid pneumonia [35] : lipoid background substance, large numbers of foamy macrophages with droplet-like cytoplasmic fat inclusions, and scant PAS-positive globular material.

BAL is the method of choice for the detection of opportunistic pulmonary infection in immunocompromised patients, particularly in patients with HIV infection and after organ transplantation. BAL may sporadically be applied in immunocompetent patients in conjunction with hospital-acquired (nosocomial) infections.

Whether an organism found in a BAL sample is pathogenic and responsible for the current lung disease must be considered in each individual case . Organisms in BAL fluids may be of no pathologic significance, in the sense of simple colonization of the mucosa, or of extraneous contamination . Diagnostic relevance for infectious disease indicates: -Bacteria included in the cytoplasm of neutrophils and macrophages -Fungi associated with marked neutrophilia and/or eosinophilia (particularly allergic bronchopulmonary aspergillosis) .

Acute bacterial pneumonia is associated with masses of neutrophils. Bacteria are ingested in the cytoplasm of neutrophils and/or macrophages. Bacteria are easily recognized in May-Grünwald-Giemsa-stained specimens and with the Gram staining procedure. z z This is the most common pulmonary infection in patients with AIDS. Pneumocystis should be considered as pathogenic whenever it has been identified.

Chapter 2  Respiratory Tract and Mediastinum z z Usually, this pathogen is detected in light microscopy by routine staining procedures (Papanicolaou and Giemsa) or by direct fluorescence stains of bronchoalveolar lavage fluids. The BAL processing mode has been shown not to affect detection of the organism, and silver staining has minor added value in the identification of pneumocysts [1, 40] . z z New molecular diagnosis using a real-time PCR assay, performed on a LightCycler system, is potentially more sensitive compared with the use of conventional cytochemical stains and light microscopy. The technique may discriminate as well between colonization and infection with pneumocysts [20] . z z Differential cytology in BAL of AIDS patients usually shows an increased number of lymphocytes and granulocytes [10] . Hyperplastic type II pneumocytes may be present.z z More information including morphologic appearance of this organism is provided in Sect. 2.1.6.3.2, "Pneumocystis," p. 118.

(see also Sect. 2.1.6.3, "Pulmonary Mycoses," p. 117) z z Candida and Aspergillus are frequently identified in cytologic samples of the lung periphery, but they often indicate a nonpathogenic colonization. These two types of fungi have been shown to be pathogens in only a low percentage of all positive cytologic findings [44] . z z Cytologic findings of cytomegalic inclusion disease is highly specific; however, cytology is not very sensitive for this type of viral pneumonia. Other laboratory techniques such as culture, immunocytochemistry, in situ hybridization, as well as new developments in PCR technology are much more sensitive [19] . z z It is a fact that highly sensitive methods may lead to overdiagnosis of CMV pneumonia because CMV is found worldwide and throughout all socioeconomic groups and infects a high proportion of the adult population without apparent illness [44] .

Herpes simplex virus, respiratory syncytial virus, or adenovirus, among others can be responsible for viral pneumonia, particularly after organ transplantation. [45] 2.3.6.1 Carcinomas z z Bronchoalveolar lavage is an extremely valuable tool in the diagnosis of diffusely spreading bronchioloalveolar carcinoma and suspected metastatic lung disease, particularly in cases with pronounced carcinomatous lymphangitis. Diagnostic accuracy ranges from 93% (bronchioloalveolar carcinoma) to 83% (lymphangiosis carcinomatosa due to metastatic cancer) [46] . z z Unlike bronchioloalveolar carcinoma, carcinomatous lymphangitis is usually accompanied by a lymphocytosis in BAL [11] .

z z BAL has turned out to be a minor help in the diagnosis of primary bronchial cancer since this type of cytologic investigation yields no additional information compared to bronchoscopy. 

The diagnostic yield of BAL in lung involvement by leukemia or malignant lymphoma ranges from about 40 to 60% [46] . Final diagnosis is reliably reached by immunocytochemical or flow cytometric phenotyping of the lymphoid cells and/or establishing clonality of the lymphoid population by immunocytochemistry or molecular tests. Lung-infiltrating Hodgkin lymphoma can reliably be diagnosed in BAL cytology if the pathognomonic tumor cells (Hodgkin and Reed-Sternberg cells) are present [39] .Caution z z It may be difficult to distinguish between inflammatory BAL lymphocytosis with evidence of reactive cell alterations and low-grade malignant non-Hodgkin lymphoma . However, the distinction should pose no major problems using differential cytology and additional analyses in order to assess monoclonality . z z It is impossible to distinguish between inflammatory BAL lymphocytosis with evidence of reactive cell alterations and the lymphoid population of lung-infiltrating Hodgkin lymphoma lacking the pathognomonic Hodgkin and Reed-Sternberg cells, neither by morphology nor by auxiliary analyses .

The terms formerly used are "histiocytosis X" and "dendritic cell histiocytosis." 

General Comments z z The mediastinum is a part of the chest cavity that extends anteroposteriorly from the posterior surface of the sternum to the spine and sagittally from the thoracic aperture to the diaphragm. The most widely used scheme to divide the mediastinum uses four compartments: superior, anterior, middle, and posterior. z z The mediastinum is an area of great interest, because it is a site of numerous organs that can become involved in various pathologic disorders (thymus, lymph nodes, ganglia, soft tissue), apart from lesions spreading from organs that are located in the mediastinum or border this space (heart, esophagus, major vessels, vertebral column, and the membranes confining the heart and lungs).z z The development of new radiologic techniques such as computerized tomography, sonography, or endoscopic ultrasound allows the chest physician extensive use of invasive preoperative diagnostic procedures such as mediastinoscopy, limited thoracotomy, transthoracic fine-needle aspiration biopsy (FNAB), and endoscopic ultrasoundguided fine-needle aspiration (EUS-FNAB). Tumorous mediastinal lesions such as tumors of the thymus, lymph nodes, ganglia, soft tissue, and others have gained interest in recent years not only to surgical pathologists, but also, to a great extent, to cytopathologists. z z Metastases are the largest category of mediastinal neoplasms diagnosed by FNAB followed by primary mediastinal tumors. Metastases usually present minor cytodiagnostic difficulties and ancillary immunocytochemical studies are helpful in assessing primary tumor location. In contrast, many primary neoplasms such as malignant lymphoma, thymoma, and germ cell tumors implicitly call for additional analyses, in order to achieve a reliable cytologic diagnosis and subclassification, or surgical biopsies [80] . 

z z Varied FNAB techniques have made the morphologic investigation of mediastinal masses not only possible, but also safe. Complications are rare including pneumothorax, hemorrhage, and hemoptysis. Pneumothorax has been reported as the most common complication [1, 34. 81] . Image-guided FNAB is becoming increasingly accepted as a diagnostic tool and as a substitute for core biopsy. This method can prevent a substantial number of more invasive surgeries, for instance mediastinoscopy and open thoracotomy. Furthermore, FNAB has been shown to be an excellent tool in diagnosing mediastinal lesions in correlation with clinical history, imaging studies, laboratory features, and with excellent team work with interventional radiologists or chest physicians performing the needle aspirations [80] . z z Diagnostic accuracy ranges from about 80% to 100% [10, 29, 41, 80] . Diagnostic yield for tumors has been shown to be roughly equal in FNAB and punch biopsies, but his-

Thymus Gland and its Diseases topathologic examination of core-needle biopsies seems to be more accurate for tumor typing [11] .z z Inadequate aspirates have been reported constituting a rate between 10 and 20% [29, 80] . Proximity of major vessels and deep-seated small lesions are major technical reasons for inadequate sampling, whereas necrosis and fibrosis are biological factors responsible for limited cellularity in aspirate smears. Bloody specimens are a third reason for inadequate cytological results. z z High specificity and sensitivity have been achieved when an experienced cytopathologist or cytotechnologist is on site to ensure the adequacy of the sample [5, 20] . Immediate on-site cytologic interpretation is an additional factor that can improve diagnostic outcome [20, 92] , but this setting is very time-consuming for cytopathologists and impracticable in a majority of institutions.z z Ancillary tests such as cytochemical staining, immunocytochemistry, and molecular pathology are helpful in increasing the diagnostic accuracy of FNAB samples. Scant cellularity, poor preservation of cellular material, and blood-rich specimens are limiting factors in this respect. Special stains are particularly useful in the presence of inflammatory lesions in order to visualize organisms, such as bacteria (Gram), mycobacteria (Ziehl-Neelsen), and fungi (periodic acid-Schiff and Crocott-Gomori methenamine-silver stain). Immunocytochemical work-up of neoplastic mediastinal masses is essential in order to confirm and subclassify primary neoplasms, and to assess the primary origin of metastases [80] . FNAB may also provide material for microbiological tests (including culture) and molecular genetic analyses. [85] Modern fiberoptic equipment enables the operator to visualize parabronchial-situated nodules molding the wall of the tracheobronchial tree. The needle is passed through the fiber-endoscope and precisely inserted through the bronchial or tracheal wall into enlarged parabronchial, hilar, and paratracheal lymph nodes.

Endoscopic ultrasound-guided FNAB (EUS-FNAB) has proved to be a highly accurate diagnostic test for suspected tumorous lesions at various sites of the body, therefore avoiding numerous invasive surgical interventions [113] . Transesophageal and transbronchial EUS-FNABs are used with a high degree of sensitivity and specificity for staging of lung cancers and for primary diagnoses of mediastinal lesions. EUS-FNAB is a highly valuable method for diagnostic evaluation of lesions, especially when other modalities have failed [21, 42, 53, 68, 106] . The intervention is usually well tolerated [10] .Transbronchial EUS-FNAB allows the operator to visualize and evaluate small intramural/submucosal-situated lesions of the bronchi, and tumors within the lung parenchyma, as well as lymph nodes and abnormal findings located in the mediastinal space [5, 35, 85] .Transesophageal EUS-FNAB has become an important tool for staging lung cancer at the time of diagnosis and for assessing diagnoses on otherwise undiagnosed pulmonary and mediastinal masses. Such lesions are usually located in the posterior areas of the mediastinum and in the upper lobes of the lung [10, 13, 21, 42, 103, 111] .

The passing of the needle into the mediastinal lesion causes contamination of cells from the bronchial/ esophageal inner layers and from bronchial glands ( [108] At our institution, we prefer the use of liquid-based thinlayer technology (Cytospin, ThinPrep) for endoscopic image-guided FNAB of mediastinal disorders. The reasons for this procedure are the following: z z The entire amount of FNAB material can be preserved. z z The thin-layer method has proved to be a perfect procedure for clinicians who are not familiar with the proper preparation and fixation technique for the aspirated material, or when a cytotechnologist is not available on site during the intervention. z z In many circumstances, the liquid-based method is superior to conventional smears with regard to clear background, monolayer cell preparation, and cell preservation.

z z An optimal preparation can be achieved for special investigations, in particular for immunocytochemistry, FISH, 

Dividing the mediastinum into four compartments is not only useful for clinical purposes, but also for pathologists, because many lesions are restricted to certain compartments and related to the individual organs: [82] Esophageal perforation is the most common cause for this uncommon but severe clinical condition frequently resulting from postoperative dehiscence of intrathoracic esophageal anastomoses. Perforation can also follow endoscopy, dilatation of the esophagus, trauma, ingestion of foreign bodies, irradiation, erosion of the esophageal wall by malignant tumors, etc. Mediastinitis may exceptionally result from lymphatic spread of infections located in tissues and organs adjacent to the mediastinum such as deep neck infections, lung abscess, subphrenic abscess, or vertebral osteomyelitis. z { Cytologic specimens contain abundant neutrophils and signs of abscess formation (degenerating neutrophils and debris). It is recommended to submit a portion of the aspirated material for microbiological studies. 

Pronounced anthracosis in mediastinal lymph nodes may induce unorthodox proliferative activity of histiocytes and enlargement of the lymph node. Aspirated material appears as a black stained mass. z { Microscopy: masses of extracellular anthracotic pigment is also included in the cytoplasm of macrophages as well as a few lymphocytes.

Amyloid deposits within the mediastinal space may give rise to reactive cell changes. Cellular atypias should not lead to a misdiagnosis of cancer [80] . Morphologic features and other attributes of amyloid are covered elsewhere in this book (Sect. 2.2.1.9.1, "Amyloid Tumor," p. 136).

Mediastinal cysts comprise 10-27% of all mediastinal tumorous disorders [50] . A variety of mediastinal cysts exist, which can be divided into two main categories:1. Congenital cysts resulting from developmental anomalies of the foregut or related embryonal structures. 2. Acquired cysts including benign cyst-like lesions and secondary cystic changes in neoplastic disorders.Transthoracic or endoscopically guided FNAB is an effective method for diagnosing cystic lesions [19, 32] . Their nature can be assessed or suspected in a number of cases as a result of the cytologic features in the aspirated cyst content.

Most of these cysts are spherical and usually unilocular, and show a strong variability in size, up to several centimeters.Cystic mature teratoma (Fig. 2.91 ) More information is available in Sect. 2.4.3.6.1, "Benign Teratoma," p. 213.

Bronchogenic cysts result from abnormal branching of the tracheobronchial tree during embryonic development. They are the most common variety of all congenital cysts found in the mediastinum and occur at any age. Bronchogenic cysts are located in the anterior mediastinum but may be present elsewhere in the mediastinal space and also within the lung parenchyma.The cyst fluid may be clear, turbid, or mucoid. Esophageal cysts contain cellular elements equal to bronchogenic cysts, except cartilage tissue and chondrocytes.

Esophageal cysts arise from noncoalescing vacuoles in the wall of the foregut during development of the esophagus. These cysts are most frequently found in children and young men.

z { Nonkeratinized stratified epithelium is most likely encountered, but varying amounts of ciliated columnar epithelial cells and ciliary tufts may be present as well.

These cystic lesions have been rarely reported [110] . Ectopic pancreatic tissue associated with cystic changes generally includes ducts, acini, and islets of Langerhans.

Mediastinal teratoma containing pancreatic tissue and pancreatic pseudocysts extending into the mediastinum have to be taken into consideration.Other congenital cystic disorders of the mediastinum that have to be included in differential diagnosis considerations are thymic cysts (described in Sect. 2.4.3.3, p. 209) and meningoceles.

Thoracic duct cyst Thoracic duct cysts are probably caused by degenerative changes or congenital harm of the thoracic duct wall followed by duct dilatation and aneurysm formation [50] . A macroscopically milky chylous fluid is a diagnostic key feature.z { A few spindle-shaped or flattened endothelial cells and a variable number of mature lymphocytes may be present in smear preparations.

Hydatid cysts are most common in the mediastinum are hydatid cysts. They are caused by the larval stage of the dog tapeworm. The cystic lesion appears unilocular and multilocular, characteristically with focal areas of calcification in the cyst wall. Microscopic features, general comments, and cautions are given in several chapters of this book, e.g. Sect. 9.1.7.3, "Hydatid Cyst," p. 590. (Fig. 2.94 ).

They can occur in the regressive course of hematomas and inflammatory process. Mediastinal pancreatic pseudocyst has been mentioned in the context of mediastinal cystic pancreatic tissue. Normal thymus in adults can show extensive cystic degeneration.

Contaminating cells from organs penetrated by the needle on its way into the cyst may cause erroneous typing of the cystic lesion ( Fig . 2 .88) [50] z z The thymus is a pure epithelial organ during the first stages of its evolution. By the end of the second month of intrauterine life, the epithelial tissue becomes secondarily infiltrated by bone marrow-derived lymphocytes and mesenchymal elements. z z The thymus gland reaches the maximum weight during puberty followed by a gradual process of fatty involution. However, the organ never completely disappears but commonly becomes cystic. z z The thymus plays an important role for the immune system and produces several hormones. Primarily undifferentiated lymphocytes -migrated from bone marrow -acquire characteristics of T cells in close contact with thymic epithelium and its microenvironment. After migration to peripheral lymphoid organs the post-thymic precursor T cells finally acquire the characteristics of mature immunocompetent T cells. The process is triggered by thymic hormones. z z The thymus is located in the anterior mediastinum but small ectopic islands of thymic tissue are found throughout the mediastinal space and are extramediastinal as well. [50] (Fig. 2 

In the past, the term "thymoma" has generally been applied to any type of tumor originating in the thymus gland: thymic neoplasms included tumors arising from thymic epithelium, neuroendocrine cells, germ cells, lymphoid cell populations, and various mesenchymal cell types, particularly adipose cells. Today, the term "thymoma" is restricted to tumors originating from the thymic epithelial cells [50] ; therefore, thymomas should be separated from other neoplasms that have their origin in the thymic gland such as carcinoid, germ cell tumors, and malignant lymphomas.There have been several varied classifications of thymic tumors up to the end of the last century. Nowadays, the most widely used classing is the 2004 WHO histological typing system [102] . (Fig. 2. There is no predilection for sex, race, and geographic area [48] . z z Thymoma can sporadically be found in unusual sites according to its particular embryologic development, descending through the neck into the mediastinum. Tumors may be located in the neck area [105] , lung [60] , pleura, and mediastinal areas other than the anterior compartment.

z z A unique feature of the tumor is its association with paraneoplastic syndromes, and in particular myasthenia gravis. 

Invasiveness and prognosis of the thymomas were shown to correlate with this classification system. Other prognostic factors include the tumor stage, tumor size, and the presence of clinical symptoms. Surgery is the principal treatment for thymomas [39, 46, 71] . z z Extrathoracic metastases are rare; the most important sites include cervical lymph nodes and liver parenchyma [48] . Epithelioid tumor cells show epithelial clustering, clearly distinguishing these tumor cells from histiocytes/mesenchymal cells. Spindle epithelial cells may mimic fibroblasts; their growth pattern is manifold such as whorls or bundles. Epithelial cells in benign thymomas may be very large and pleomorphic but lack clear signs of malignancy. Architectural features include rosettes, glandular and papillary structures, perivascular spaces, and Hassall corpuscles. Squamous epithelial cells and myoid cells may also be observed and glands may be lined by goblet cells or ciliated epithelium. [4, 14, 28, 97, 98, 107] (Fig. 2.98) A biphasic population of epithelial cells and lymphocytes in varying proportions is a key feature for the cytologic diagnosis of thymoma. z { Epithelioid epithelial cells (Fig. 2.95B) 

Presence of focal cellular atypias, cellular pleomorphism, and increased mitotic activity is of limited value for estimating invasive behavior and prognosis of thymomas by cytology [14, 84, 107] .

Thymic Carcinoma [33, 56] z z Thymic neoplasms that exhibit unequivocal cytologic features of malignancy should be classified as thymic carcinoma. They have all the characteristics of malignant behavior, both histologically and clinically. Thymic carcinomas account for only a small group of the mediastinal neoplasms. A great number of morphologic variants have been reported [102] , whereas squamous cell carcinoma has proved to be the most common entity among thymic carcinomas. The histologic and cytologic features of thymic carcinoma variants as listed below are indistinguishable from corresponding tumors arising in a variety of other organs throughout the body.

z { General cytological and background features include pronounced cellular and nuclear pleomorphism, prominent nucleoli, numerous and bizarre mitotic figures, tumor necrosis, inflammatory infiltrate [7] . z { We refer to other chapters of this book regarding the cytologic pattern of particular tumor types and ordinary differential diagnosis considerations: − Squamous cell carcinoma (Fig. 2.101 

Immunocytochemistry [18, 99] 

The thymocytic tumor cell exhibit a bilineage pattern of epithelial and lymphocytic antigens. On the one hand, they show varied epithelial markers such as EMA and different cytokeratins (e.g., AE1/AE3, Cam 5.2, CK5/6, CK7, CK14, CK19), and on the other hand CD20 or CD57. The accompanying lymphocytes usually express an immature T-cell phenotype showing variable reactivity for several T-cell antigens (e.g., CD1a, CD3, CD5, CD4, CD8, CD99, TdT).CD5 and CD117 have been reported to express positive immunoreactivity in a high percentage of thymic carcinoma cells in contrast to thymoma cells. Furthermore, CD205 and Foxn1 have been proposed as a sensitive and specific marker for benign and malignant thymoma. The sensitivity of CD205 seems to be lower than CD5 and CD117 for thymic carcinoma, and Foxn1 was found to be superior Flow Cytometry Flow cytometric immunophenotyping of the lymphoid cell population may be helpful in preoperative diagnosis of thymomas, excluding benign thymic tissue and other types of thymic tumors [78] . CD4/CD8 coexpression on the lymphocytes in thymic tumors assessed by fluorescence-activated cell sorting analysis is an additional indicator for the diagnosis of thymoma [27, 28, 70, 114] . Furthermore, flow cytometric analysis on the lymphocytic population appears to be useful to determine the malignant potential of thymomas [62, 114] . Enzyme Immunoassay in Cystic Fluids Elevated CA-125 content in the fluid obtained from a cystic mediastinal tumor may be helpful in classifying the lesion as thymoma [76] .Differential Diagnosis [28, 80] The most frequent differential diagnoses of thymomas are listed next, together with immunocytochemical markers proved to be the most helpful: z z Thymomas with a dominant epithelioid component may be confused with − Primary mediastinal neoplasms: germinomas, embryonal carcinoma (placental alkaline phosphatase +), thymic carcinoid (neuroendocrine markers +); admixture of a lymphoid cell population may occur, particularly with germ cell tumors (seminoma/dysgerminoma). − Any metastatic carcinoma and melanoma (melanomatypical markers +) to the mediastinum. TTF-1 may be expressed immunocytochemically in pulmonary adenocarcinomas but not in thymoma cells [77] . − Thyroid papillary carcinoma (TTF-1 and thyroglobulin +) if the nuclei of a thymoma exhibit pale chromatin, small nucleoli, nuclear crowding and cytoplasmic invaginations [51, 67] . − Lymphocyte-rich thymoma that contains numerous transformed lymphoid elements of the B phenotype (benign lymphoblasts) may be mistaken for large-cell B-type non-Hodgkin lymphoma infiltrating the thymus gland [25, 115] . − A small-cell lymphoid infiltrate may simulate lymphoblastic non-Hodgkin lymphoma, which is a disease that affects predominantly children and young adults. The vast majority of these tumors are of T-cell lineage. Caution z z Primaries in remote organs metastasizing to the thymic gland and mediastinum must be unambiguously excluded before assessing a diagnosis of primary thymic carcinoma by cytology . The peak incidence of thymic carcinoids is in the fifth decade and is more frequent in male patients. Endocrine disorders are observed in about half of the patients afflicted with thymic carcinoid [50] . z z In contrast to thymomas, thymic carcinoids do not present with an explicit encapsulation, they are frequently invasive to adjacent structures, and show frequent metastases to regional lymph nodes and distant organs. Thymic carcinoid has an overall poor prognosis [65] . Focal hemorrhage and necrosis, but not cystic degeneration, may be present. 

z z Thymoma has been reported as the most frequent misdiagnosis in the presence of a carcinoid tumor of the thymus (Fig. 2.102) . Cells of carcinoid tumors may share morphologic features with epithelioid cells of thymomas, but the frequent occurrence of pyknotic cells in carcinoids mimicking lymphocytes seems to be the main reason for misdiagnosis between carcinoid tumor and thymoma [83] . Immunocytochemical reactivity for neuroendocrine markers (synaptophysin, chromogranin, CD56) should help in the correct assignment of a thymic carcinoid tumor [101] ; however, positivity for neuroendocrine markers is occasionally achieved in thymic carcinomas as well. Further immunostainings that may be helpful to distinguish thymoma from carcinoid tumor are p63 and CK5/6 (positive on thymoma and thymic carcinoma, negative on carcinoids) and CD5. CD5 yields a positive reaction in half of the thymic carcinomas and is suitable in distinguishing poorly differentiated carcinoids [83] . z z Adenocarcinomas represent characteristic cytomorphologic features including single cells, compact spherical and acinar clusters, large eccentric nuclei, prominent nucleoli, thinly dispersed chromatin, and usually a low N/C ratio. Certain monomorphic adenocarcinomas of the gra-nular cell type may provoke differential diagnosis problems, such as metastasis of renal cell carcinoma and thyroid carcinoma (among others). [17, 112] General Comments 

Mediastinal metastases from a primary germ cell tumor of the gonads must always be excluded by clinical and radiographic examination of the testes/ovaries and retroperitoneal lymph nodes, and the patient's history .

z z Mature teratomas are predominantly cystic (Fig. 2.91 ). They are composed of tissue elements usually derived from all three germ layers. z z Immature teratomas occur extremely rarely in the mediastinum and are particularly characterized by the presence of immature squamous cells and mesenchymal cells. [3, 15, 45, 58] (Fig. 12.38 ) Seminoma in the mediastinum occurs nearly exclusively in men and is the most common malignant germ cell tumor at this site. Seminomas have a better prognosis compared to other malignant germ cell tumors of the mediastinum because they are highly sensitive to radiation therapy. 

Syncytiotrophoblast-like multinucleated giant cells of histiocytic origin should not mislead the cytopathologist to a diagnosis of choriocarcinoma . Syncytiotrophoblasts are immunocytochemically positive for β-human chorionic gonadotropin and giant cells of histiocytic origin exhibit CD68 antigen . [15, 28, 45] z z Placental alkaline phosphatase (PLAP) is a reliable immunomarker for germinoma on cytological preparations ( Fig. 12.38D ). z z Non-Hodgkin lymphoma of the large-cell type is a major challenge in the differential diagnosis with seminoma, particularly in cases of lymphoma with a tendency to cellular cohesion. Large-cell lymphoma with a reactive hyperplastic population of T-lineage lymphocytes should not exhibit plasma cells.

In cytomorphologically equivocal cases, immunocytochemistry is of major help: large-cell lymphoma cells are usually positive for CD45 and in most cases for Bcell markers. Positive immunoreaction for leukocyte/lymphocytic markers is definitely absent in germinomatous cells.

Choriocarcinoma [2, 15, 57, 58] These variants of germ cell tumors rarely arise in the mediastinum. Microscopic and immunocytochemical characteristics of these entities are provided in Sect. 12.3.7, "Germ Cell Tumors," p. 784, and 

Lymphoblastic Lymphoma (Fig. 15 .43) Cells of this high-grade malignant lymphoma usually exhi bit the T-cell immunophenotype. Lymphoblastic lymphoma is the most common malignant lymphoma in children and young adults (particularly in males) and concomitantly a rather common cause of mediastinal mass in this age group [95] . A majority of the tumors arises in the thymus. Acute T-cell leukemia may occur during the course of the disease. [115] .

Lymphocyte-rich thymoma could be misdiagnosed as lymphoblastic lymphoma. This is a challenging differential diag-Chapter 2  Respiratory Tract and Mediastinum nosis, particularly in cases where the tumor cells are intermingled with residual thymic epithelial components. But the typical appearance of the neoplastic lymphoblasts and the clinical features should provide enough evidence for a correct diagnosis.Large-Cell Non-Hodgkin Lymphoma [89, 96] (Figs. 2.107 and 2.108) Large-cell non-Hodgkin lymphoma of the mediastinum represents in most cases a distinct tumor entity arising from a native thymic B-cell population, unless mediastinal involvement is part of a systemic malignant lymphoid disorder. The primary mediastinal disorder occurs typically in a young adult patient group with a female preponderance [95] and suggests a more favorable course than that of diffuse large B-cell lymphoma [89] . [36, 37, 93] z { The aspirates are usually highly cellular, composed of predominantly large atypical lymphocytes scattered throughout the smear; small cleaved atypical lymphocytes tend to be intermingled in a varying number. Differential Diagnosis and Immunocytochemistry [28, 93, 115] z z Paucity of cells due to strong tumor sclerosis may: − lead to a false-negative diagnosis. − suspect spindle cell neoplasia such as soft tissue sarcoma, nerve sheath tumors, spindle-cell thymoma, spindle-cell melanoma. All these tumor entities express tissue-typical markers but not CD45. z z Cohesive cell grouping in specimens of non-Hodgkin lymphoma may be confused with thymic carcinoma or metastatic carcinoma (Fig. 2.107 ). 

Cytomorphology and immunophenotyping are complemental investigations in order to distinguish between reactive lymphoid lesions and malignant lymphomas of the mediastinum . But the limitations of these two basic tests should always be remembered regarding: -FNAB samples with limited cellularity .-Partial tumor infiltration of a lymph node or of an organ with an important benign lymphoid proportion . -Hodgkin lymphoma comprising a strong reactive lymphoid background together with a poor specific tumor cell fraction . -Malignant lymphomas of the T-cell phenotype .

z z Neurogenic tumors are the most common neoplasias arising in the posterior mediastinum. Nerve sheath tumors and paragangliomas are more frequent in the adult patient group, whereas tumors of the sympathetic nervous system are frequently encountered in children.z z Any mesenchymal tumor may arise in the mediastinal soft tissue (Fig. 2.109) . Only a few cases are on record concerning cytological investigation using fine needle aspirates. Benign mesenchymal lesions comprise, among others, lipomas, hemangiomas, and lymphangiomas [16] . Primary sarcomas are rare; however, a few case reports on FNAB of liposarcoma are available in the literature [28, 59, 73, 94] .