key: cord-0271881-x529fnie authors: Batah, S.; Benatti, M.; Siyuan, L.; Telini, W.; Barbosa, J.; Menezes, M.; Nadai, T.; S, K.; Vaswani, C.; Gupta, S.; Zamboni, D.; Wada, D.; Calado, R.; Oliveira, R.; Louzada-Junior, P.; Auxiliadora-Martins, M.; Veras, F.; Cunha, L.; Cunha, T.; Luppino-Assad, R.; Balancin, M.; Morais, S.; Martins, R.; Arruda, E.; Chahud, F.; Koenigkam-Santos, M.; Cetlin, A.; Cunha, F.; Santos, C.; Capelozzi, V.; Fukuoka, J.; Duarte-Achcar, R.; Fabro, A. title: COVID-19 Bimodal Clinical and Pathological Phenotypes date: 2021-09-14 journal: nan DOI: 10.1101/2021.09.03.21262841 sha: 7a22dc09751bfb4d45ac56d2d03ddff8fc695ad3 doc_id: 271881 cord_uid: x529fnie Background Patients with coronavirus disease-2019 (COVID-19) present varying clinical complications. Different viral load and host response related to genetic and immune background are probably the reasons for these differences. We aimed to sought clinical and pathological correlation that justifies the different clinical outcomes among COVID-19 autopsies cases. Methods Minimally invasive autopsy was performed on forty-seven confirmed COVID-19 patients from May-July, 2020. Electronic medical record of all patients was collected and a comprehensive histopathological evaluation was performed. Immunohistochemistry, immunofluorescence, special stain, western blotting and post-mortem real-time reverse transcriptase polymerase chain reaction on fresh lung tissue were performed. Resultss We show that 5/47 (10,6%) patients present a progressive decline in oxygenation index for acute respiratory distress syndrome (PaO2/FiO2 ratio), low compliance levels, interstitial fibrosis, high -SMA+ cells/protein expression, high collagens I/III deposition and NETs(P<0.05), named as fibrotic phenotype (N=5). Conversely, 10/47 (21,2%) patients demonstrated progressive increase in PaO2/FiO2 ratio, high pulmonary compliance levels, preserved elastic framework, increase thrombus formation and high platelets and D-dimer levels at admission (P<0.05), named as thrombotic phenotype. While 32/47 (68,1%) had a mixed phenotypes between both ones. Conclusions We believe that categorization of patients based on these two phenotypes can be used to develop prognostic tools and potential therapies since the PaO2/FiO2 ratio variation and D-dimer levels correlate with the underlying fibrotic or thrombotic pathologic process, respectively; which may indicate possible clinical outcome of the patient. The Severe Acute Respiratory Syndrome Coronavirus-2 (SARS-CoV-2) was first reported in Wuhan in China in 2019 1 . Infected patients can experience the less severe typical flu-like symptoms with fever, dry cough, and dyspnea 2 . However, in more severe cases, patients require intensive care unit (ICU) admission and mechanical ventilatory support. Acute respiratory distress syndrome (ARDS) is a major complication for severely infected patients and can lead to multi-organ failure such as acute kidney injury, cardiac complications and thromboembolic events 3 4 . Differences in these outcomes can be attributed to a differential host response to infection with variable viral load, age, gender, comorbidities, genetic and immune background. While different studies have stratified heterogenous COVID-19 patients based on ABO blood grouping 5 , cancer subtypes 6 , hyper-inflammatory 7, 8 , the characterization of histopathological phenotypes in COVID-19 patients could reveal the underlying pathophysiological process, but it remains largely unreported. Studies describing the clinical progression of patients who died from COVID-19 correlated to their histopathological pattern are still lacking. We hypothesized that SARS-CoV-2 infection can lead to different mechanisms of lung injury/repair with different clinical and ventilatory manifestations, even though they all lead to patient death. Therefore, we aimed to assess whether there is a clinical and pathological basis that could explain the different clinical outcomes among COVID-19 patients with commonly associated long-term lung dysfunction. Here we present a unique histopathologic analysis of COVID-19 autopsy cases with clinical and pathological correlation and demonstrate a distinct bimodal phenotypic characterization. . CC-BY-NC-ND 4.0 International license It is made available under a perpetuity. is the author/funder, who has granted medRxiv a license to display the preprint in (which was not certified by peer review) preprint The copyright holder for this this version posted September 14, 2021. ; https://doi.org/10.1101/2021.09.03.21262841 doi: medRxiv preprint Forty-seven consecutive COVID-19 patients with positive nasopharyngeal swab for SARS-CoV-2 by reverse transcription polymerase chain reaction (RT-PCR) were considered eligible for this study. Modified minimally invasive autopsy (MIA) 9 was performed at University Hospital of Ribeirão Preto Medical School, University of São Paulo, Ribeirão Preto, SP, Brazil -HCFMRP/USP from May to July, 2020. Briefly, all MIAs were performed at bedside through post-mortem surgical lung biopsy within 1 hour of death by a 3 cm incision on the anterior side of the chest between the fourth and fifth ribs. A matching 14-gauge cutting needle (Magnum Needles, Bard) and a biopsy gun (Magnum, Bard) also were used. Two post-COVID-19 biopsies cases were included. This study was approved by the local Research Ethics Committee and written informed consent was waived. Electronic medical record of all patients (N=47) enrolled in this study was collected. Demographic, clinical data, symptoms, drugs, treatments prescribed and laboratory tests were recorded thoroughly. Laboratory tests were collected and identified as: 1) Admission tests: up to the first 48 hours of admission; and 2) Daily tests: on the fifth, third and first day before death. In order to better understand patient's outcome, mechanical ventilation parameters of each individual patient were recorded. All daily change of these variables (from the first to the last day of mechanical ventilation until death) were registered and the means recorded for the last day before death of each individual. In addition, PaO2/FiO2 linear regression was performed with all available values. Then, to determine which patients had changes of lung function, we calculated the larger and smaller angles from the lines . CC-BY-NC-ND 4.0 International license It is made available under a perpetuity. is the author/funder, who has granted medRxiv a license to display the preprint in (which was not certified by peer review) preprint Lung tissue samples were fixed in 10% buffered formalin, for at least 48 h. Paraffin-embedded sections of 3-μm thickness were stained with Haematoxylin and Eosin, Picrosirius red (Abcam, ab150681) for collagen fibers identification and Verhoeff (Abcam, ab150667) for elastic fibers identification, according to local protocol. Immunohistochemistry for anti-alpha smooth muscle actin (α-SMA) (Abcam, ab5694) and anti-SARS-CoV-2 polyclonal antibody, developed by our group for in situ detection of SARS-CoV-2, were performed in paraffin-embedded sections of 3-μm thickness, following our lab protocol 10 . Histological evaluation was performed by specialized pulmonary pathologists (MLB, VLC, ATF) blinded to clinical history. For all patients, histopathological features were assessed as present or absent. Cut-offs of area involvement were determined for fibrotic phenotype, OP and AFOP, while thrombus formation was considered present or absent. Histochemistry and immunohistochemistry stains were quantified by morphometry. The images were captured with a digital camera on microscope (Novel L3000 LED) and analyzed using Image Pro Plus 7 software. Quantification followed the morphometric standards established by American Thoracic Society and European Thoracic Society (ATS/ERS) 11 . Positive α-sma cells were evaluated in ten different, randomly selected high-power fields of the lungs. At 400x magnification, the number of . CC-BY-NC-ND 4.0 International license It is made available under a perpetuity. is the author/funder, who has granted medRxiv a license to display the preprint in (which was not certified by peer review) preprint The copyright holder for this this version posted September 14, 2021. ; https://doi.org/10.1101/2021.09.03.21262841 doi: medRxiv preprint positive cells in each field was calculated according to the number of points hitting positive cells as a proportion of the total grid area. The density of collagen and elastic fibers was measured in the lung parenchyma in ten randomly selected microscopic fields at a magnification of ×200. The threshold for collagen fibers was established for all slides after the contrast was enhanced to the point at which the fibers were easily identified as green or orange bands. The density of the collagen and elastic fibers was expressed as the ratio between the measured fibers divided by the total area studied ×100. Neutrophils and neutrophil-derived extracellular traps (NETs) were identified and quantified by immunofluorescence with anti-myeloperoxidase (MPO) (Abcam, ab25989), anti-citrullinated histone H3 (H3Cit) (Abcam, ab5103) and DAPI (Life Technologies, D1306). The staining and quantification were performed as our lab protocol 12 . Protein extraction were performed for all fresh lung samples using QIAzol Lysis Reagent (Qiagen), according to our standered protocol. Protein levels were measured with the Bio-Rad Protein Assay (cat. 5000006) and transferred into a nitrocellulose membrane (GE Healthcare Biosciences, cat. 10600002). The membranes were incubated with antiα-SMA (Abcam, ab7817), anti-matrix metalloproteinase-2 (anti-MMP-2) (Abcam, ab97779) and anti-glyceraldehyde-3-phosphate dehydrogenase (anti-GAPDH) (Abcam, ab9485). The proteins were detected and quantified with ChemiDoc Imaging Systems (Bio-Rad) and the results were normalized by GAPDH expression. is the author/funder, who has granted medRxiv a license to display the preprint in (which was not certified by peer review) preprint 13 and Charité Germany 14 , respectively. Samples were tested in triplicate and cycle threshold values less than 44 were considered positive. Statistical analysis was performed with SPSS v.13.0 0 software (SPSS, Inc., Chicago, IL, 2004). The data was evaluated using T test. Furthermore, nonparametric correlation (Spearman) was also performed with all collected data. Linear regression was also performed for these patients with all available PaO2/FiO2 values. Data are expressed as mean ± standard deviation and the p value less than 0.05 was be considered statistically significant. 47 COVID-19 cases were confirmed by RT-PCR from nasopharyngeal swab. Table 1 . is the author/funder, who has granted medRxiv a license to display the preprint in (which was not certified by peer review) preprint The copyright holder for this this version posted September 14, 2021. ; https://doi.org/10.1101/2021.09.03.21262841 doi: medRxiv preprint The mean time from the onset of symptoms to death was 18.9 days with a mean hospital length of stay of 14.4 days. Patients were equally distributed by gender and the mean age was 67.8. Preexisting medical comorbidities were present in all patients, with systemic arterial hypertension as the most common (55%) followed by obesity (36%). The most frequent initial symptom was cough (55%). Dyspnea was present before the admission (66%), at the time of admission (79%), and during the hospital stay (40%). Clinical complications post hospital admission includes septic shock (62%), acute renal failure (51%) and acute respiratory distress syndrome (ARDS) (45%). Retrospective review of chest X-ray (CXR) and high-resolution computed tomography (HRCT) of the chest was performed for all patients. On hospital admission, ground-glass opacities (GGO) were found in all 47 cases, and interstitial opacities were noted in 23 cases (48.9%). Consolidations were present in 13 of 15 cases (87%). Additional findings include traction bronchiectasis (N=6; 40%) and architectural distortion (N=8; 53.3%) (Supplementary Table 1 ). Retrospective review of in-hospital treatments includes the use of steroids (81%) and prophylactic anticoagulation therapy (100%). Initial laboratory tests, collected in the first 48 hours post admission, demonstrated increased values of lactate dehydrogenase, C-reactive protein and D-dimer (Table 1) . Additional laboratory tests are described in Supplementary Table 2 . Mechanically ventilated patients (N=36, 76.6%), received neuromuscular blockade and prone positioning treatment (Table 1 ). PaO2/FiO2 ratio statistically correlated with D-dimer levels (r=0.37; P<0.05) ( Supplementary Fig. 1A ). . CC-BY-NC-ND 4.0 International license It is made available under a perpetuity. is the author/funder, who has granted medRxiv a license to display the preprint in (which was not certified by peer review) preprint The copyright holder for this this version posted September 14, 2021. ; https://doi.org/10.1101/2021.09.03.21262841 doi: medRxiv preprint The PaO2/FiO2 linear regression, based on daily measure from the last value recorded for PaO2/FiO2 (before death) to the onset of mechanical ventilation, showed a bimodal clinical-pathological phenotype ( Table 2): 1) Fibrotic Phenotype (N=5)characterized by progressive decline in PaO2/FiO2 ratio and low compliance levels during hospitalization ( Figure 1A ); and alveolar septal thickening with myxoid fibrosis typical to an organizing-phase of diffuse alveolar damage (DAD) ( Figure 1C ; Table 3 ). Compliance correlated negatively with drive pressure for fibrotic phenotype (r=-0.67; P<0.05) ( Supplementary Fig. 1C ). PaO2/FiO2 ratio and high pulmonary compliance levels during hospitalization ( Figure 1B ); and resolution of the acute/subacute lung injury to near to normal or slight distortion of the underlying lung parenchyma architecture ( Figure 1D ; Table 3 ), and with high frequency of thrombosis ( Figure 1D ). Clinical and radiological data from both phenotypes are described in Supplementary Tables 4 to 6 . D-dimer and platelets count was significantly higher in patients with thrombotic phenotype compared to fibrotic phenotype (Supplementary Fig. 2A , B and Supplementary Table 5 ; P <0.05). Findings from CRX image study showed similar distribution between bimodal phenotypes (Supplementary Table 6 ). A detailed histomorphological review of 47 MIA was performed to better understand COVID-19 induced lung injury (Supplementary Table 3 ). Variable amounts of alveolar septal thickening by fibrosis (interstitial fibrosis) were identified as the most common feature affecting the majority of the patients (N=41; 87.2%) (Supplementary Table 3 ). These findings significantly correlated with PaO2/FiO2 ratios (r=-0.42; P<0.05) ( Supplementary Fig. 1B) . In our cohort of 47 patients, we observe a unique bimodal is the author/funder, who has granted medRxiv a license to display the preprint in (which was not certified by peer review) preprint phenotypes. This population seems to represent an intermediate non-bimodal phenotype that appears to fall between two opposite ends manifesting as fibrotic and thrombotic respectively ( Figure 1E ). They may represent an intermediate phenotype showing different stages of involvement acute/subacute lung injury and fibrotic DAD morphologic features including organizing pneumonia (OP), acute fibrinous and organizing pneumonia (AFOP) with intra-alveolar fibrin "balls", and variable amounts of interstitial scarring. Interestingly, a moderate to low frequency of thrombosis was noticed in these patients ( Figure 1E ). The fibrotic phenotype demonstrated in our cohort appears to be triggered by an imbalance between degradation and production of extracellular matrix (ECM) by myofibroblastic activation. Severe decrease in ECM elastic fibers was found in lungs from patients presenting the fibrotic phenotype, contrasting with the preserved elastic framework seen in lungs from patients with the thrombotic phenotype, as highlighted by Verhöeff staining (P<0.05) (Figure 2A, B) . This is further supported by the presence of a direct association between the area fraction of elastic fibers in ECM and the compliance levels during mechanical ventilation (r=0.57; P<0.05) ( Supplementary Fig. 1D ). The fibrotic phenotype patients showed prominent accumulation of α-SMA in ECM, a marker of myofibroblast activity and neovasculogenesis, compared to thrombotic phenotype patients (P <0.05) (Figure 2A is the author/funder, who has granted medRxiv a license to display the preprint in (which was not certified by peer review) preprint The copyright holder for this this version posted September 14, 2021. Picrosirius Red staining demonstrated a significant increase in ECM deposition by green-birefringence thin fibers (most by types III collagen) and red/orangebirefringence thick fibers (most by type III collagen) in lungs from patients with fibrotic phenotype (P<0.05) ( Figure. 3B, C) . These findings significantly correlate with PaO2/FiO2 ratios (r=-0.64; P<0.05) (Supplementary Fig. 1F) . Additionally, neutrophils with significantly higher length of NETs were also observed in these patients (P<0.05) ( Supplementary Fig. 3A , C). We discovered two distinctive histopatholgical bimodal phentoypes and correlated histopathologic findings to corresponding clinical outcomes. Patients presenting with confirmed lung fibrosis predominantly displayed either thrombotic or fibrotic characterization, which correlated to differing clinical outcomes. This is in contrast to the initial pathophysiological events that occur in the acute phase of ARDS is the author/funder, who has granted medRxiv a license to display the preprint in (which was not certified by peer review) preprint Upon viral insult to the airways and bronchial epithelial cells, a severe lymphocytic bronchiolitis occurs, promoting epithelial injury and cell death, eventually resulting in structural disarray by airway-centered remodeling ( Figure 5 ). The aggressive airway wall infection then spreads to the lung parenchyma, inducing cellular pneumonitis, and damages the alveolar-capillary barrier ( Figure 5, yellow arrow) . This promotes the denudation of the alveolar septa, characterized as DAD, bronchiolocentric alveolar hemorrhage or fibroblastic plug, called OP, associated or not with fibrin balls, known as AFOP ( Figure 5 ). Subsequently, two different outcomes of repair appear to occur depending on resolution or progression of the lung injury, eventually manifesting as a thrombotic phenotype with gradual recovering of the acute/subacute lung injury associated with thrombosis; or a fibrotic phenotype with sustained myofibroblastic proliferation with interstitial scarring and parenchymal remodeling (Figure 1, 5) . The fibrotic phenotype seen in some patients is the end are the result of the activation and termination of many different pathways, one of which is collagen fibers deposition (type I and III) to cause alveolar septal thickening ( Figure 3) . Additionally, the fibrotic phenotype revealed higher active myofibroblasts α-SMA area fraction ( Figure 2A , C) and higher α-SMA and MMP-2 expression ( Figure 2D ) (P <0.05) than the thrombotic phenotype. Similar studies also describes COVID-19 organizing DAD with α-SMA+ myofibroblasts 15 and fibrous parenchyma remodeling 16, 17 . Alveolar septal thickening by fibrosis impairs adequate lung function and gas exchange, which is reflected in our study by significant correlation between collagen fibers deposition and PaO2/FiO2 ratio in the fibrotic phenotype (r=-0.64; P <0.05) (Supplementary Fig. 1F ). Furthermore, lung elastic capacity, represented by elastic fibers area fraction (Verhoeff is the author/funder, who has granted medRxiv a license to display the preprint in (which was not certified by peer review) preprint The copyright holder for this this version posted September 14, 2021. ; https://doi.org/10.1101/2021.09.03.21262841 doi: medRxiv preprint stain quatification) was significantly reduced (P<0.05) (Figure 2A, B) . Moreover, fibrotic phenotype patients presented NETs in a significantly higher extent throughout lung parenchyma compared to thrombotic phenotype subjects (P<0.05) (Supplementary Fig. 3 ). As described by our group previously 12 , the formation of neutrophil extracelular traps (NETs), networks of extracellular fibers, primarily composed of DNA from neutrophils, binded with pathogens 18 , is an important response to SARS-CoV-2 during the acute and a potential contributory factor to later fibrotic phase by amplify the chronic reparative phase. This result suggests a more prominent host inflammatory response in the fibrotic phenotype subjects with consequently greater damage to lung parenchyma, trigging a more aggressive reparative fibroblastic process, as observed in these patients. In accordance with the histological analysis, the clinical data also suggested a poor clinical outcome. These patients presented progressive decline in PaO2/FiO2 ratio ( Figure 1A) (mean 101.16) and low compliance levels during hospitalization (mean 19.8 ml/cmH2O) ( Table 2 ). In accordance to other studies, low ventilatory parameters were also (Table 2) . Similarly, a nearly normal lung compliance has also surprised Gattinoni et al 22 as their patients presented 50.2 ml/cmH2O, despite the severe hypoxaemia. However, better ventilatory parameters in our thrombotic phenotype subjects could be justified by the gradual recovering of the acute/subacute lung injury ( Figure 1D ) with increased area fraction of elastic fibers (Figure 2A, B) . Nevertheless, sudden death occurred, probably due to higher frequency of pulmonary thromboembolism ( Figure 1D , Table 3 ), as also described in other studies 23,24 . As is the author/funder, who has granted medRxiv a license to display the preprint in (which was not certified by peer review) preprint The copyright holder for this this version posted September 14, 2021. ; https://doi.org/10.1101/2021.09.03.21262841 doi: medRxiv preprint expected, D-dimer levels and platelets count were significantly higher in these patients than in fibrotic phenotype subjects ( Supplementary Fig. 2A However, our work provides insight into the importance of histopathological screening among COVID19 autopsies correlated to their differing clinical outcomes, with a particular focus in the lung repair resolving phase of injury. Besides those two crucial phenotypes, it is important to mention that 32 patients (68%) had a mixed pattern of lung injury appearing as a non-bimodal phenotype ( Figure 1E ). The pathophysiology of these patients probably represents different stages of viral lung injury, with both features of acute/subacute and fibrotic/organizing lung injury with variable degrees of interstitial scarring, OP and AFOP. Despite the importance of this histopathological finding, the correlation with clinical data did not highlight any relevance. On the other hand, the clinical and pathological correlation of our 15 patients is the author/funder, who has granted medRxiv a license to display the preprint in (which was not certified by peer review) preprint The copyright holder for this this version posted September 14, 2021. The authors declare no competing financial interests. . CC-BY-NC-ND 4.0 International license It is made available under a perpetuity. is the author/funder, who has granted medRxiv a license to display the preprint in (which was not certified by peer review) preprint The copyright holder for this this version posted September 14, 2021. is the author/funder, who has granted medRxiv a license to display the preprint in (which was not certified by peer review) preprint is the author/funder, who has granted medRxiv a license to display the preprint in (which was not certified by peer review) preprint The copyright holder for this this version posted September 14, 2021. is the author/funder, who has granted medRxiv a license to display the preprint in (which was not certified by peer review) preprint is the author/funder, who has granted medRxiv a license to display the preprint in (which was not certified by peer review) preprint is the author/funder, who has granted medRxiv a license to display the preprint in (which was not certified by peer review) preprint The copyright holder for this this version posted September 14, 2021. ; is the author/funder, who has granted medRxiv a license to display the preprint in (which was not certified by peer review) preprint The copyright holder for this this version posted September 14, 2021. ; https://doi.org/10.1101/2021.09.03.21262841 doi: medRxiv preprint in PaO2/FiO2 ratio (A), and significant alveolar septal thickening by fibrosis (Cdouble blue arrows, E) without thrombus formation (C); and 2) Thrombotic Phenotype (N=10) showing progressive increase in PaO2/FiO2 ratio (B), and resolution of acute/subacute lung injury to normal or near to normal parenchyma architecture and thrombus formation on vessels (D, E) . A population showing a mixed phenotype of lung injury (N=31) with morphologic features from both fibrotic and thrombotic phenotypes, including but not limited to organizing pneumonia, acute and fibrinous organizing pneumonia, and variable amounts of interstitial scarring, was present. This population seems to represent an intermediate non-bimodal phenotype, showing involvement by different stages of acute, organizing, and fibrotic DAD, that appears to fall between two opposite ends of lung injury manifesting as fibrotic and thrombotic respectively. Interestingly, a moderate to low frequency of thrombosis was noticed in these patients (E). . CC-BY-NC-ND 4.0 International license It is made available under a perpetuity. is the author/funder, who has granted medRxiv a license to display the preprint in (which was not certified by peer review) preprint Extensive collagen production and interstitial deposition was noted, characterized by the presence of alveolar septal expansion by dense fibrosis (yellow arrows), which was more prominent in the fibrotic phenotype, confirmed by picrosirius red staining (Ayellow . CC-BY-NC-ND 4.0 International license It is made available under a perpetuity. is the author/funder, who has granted medRxiv a license to display the preprint in (which was not certified by peer review) preprint The copyright holder for this this version posted September 14, 2021. ; https://doi.org/10.1101/2021.09.03.21262841 doi: medRxiv preprint arrow). Area fraction percentage of collagen fibers labeled by green and yellow orangepolarized picrosirius red stain was significantly higher in fibrotic phenotype compared with thrombotic one, as demonstrated by P <0.05 (B, C) . is the author/funder, who has granted medRxiv a license to display the preprint in (which was not certified by peer review) preprint The copyright holder for this this version posted September 14, 2021. ; https://doi.org/10.1101/2021.09.03.21262841 doi: medRxiv preprint There is minimal chronic inflammation and airway wall and lung parenchyma remodeling, characterized by submucosal scarring and alveolar septal thickening by fibrosis associated with alveolar pneumocyte prominence, respectively. While this may represent scarring secondary to resolving infection, the possibility of an evolving post infection chronic fibrosing disease needs to be excluded and more extensive studies are needed to investigate post COVID-19 complications in patients who survive the disease. is the author/funder, who has granted medRxiv a license to display the preprint in (which was not certified by peer review) preprint The copyright holder for this this version posted September 14, 2021. ; https://doi.org/10.1101/2021.09.03.21262841 doi: medRxiv preprint is the author/funder, who has granted medRxiv a license to display the preprint in (which was not certified by peer review) preprint The copyright holder for this this version posted September 14, 2021. ; https://doi.org/10.1101/2021.09.03.21262841 doi: medRxiv preprint acute DAD, and fibrin balls associated with fibroblastic plugs of organizing pneumonia, known as acute fibrinous and organizing pneumonia. Subsequently, two different ultimate ends of repair appear to occur depending on resolution or progression of the lung injury, eventually manifesting as a thrombotic phenotype, with gradual recovering of the acute/subacute lung injury associated with prominent thrombosis; or a fibrotic phenotype with sustained myofibroblastic proliferation, which promotes interstitial scarring and parenchymal remodeling. is the author/funder, who has granted medRxiv a license to display the preprint in (which was not certified by peer review) preprint The copyright holder for this this version posted September 14, 2021. ; https://doi.org/10.1101/2021.09.03.21262841 doi: medRxiv preprint Risk Factors Associated With Acute Respiratory Distress Syndrome and Death in Patients With Coronavirus Disease Clinical Features of 85 Fatal Cases of COVID-19 from A Retrospective Observational Study COVID-19 pneumonia: different respiratory treatments for different phenotypes? Intensive care medicine Forty Postmortem Examinations in COVID-19 Patients Genomewide Association Study of Severe Covid-19 with Respiratory Failure. The New England journal of medicine COVID-19 prevalence and mortality in patients with cancer and the effect of primary tumour subtype and patient demographics: a prospective cohort study. The Lancet. Oncology Human cardiosphere-derived stromal cells exposed to SARS-CoV-2 evolve into hyper-inflammatory/pro-fibrotic Minimally invasive autopsy: an alternative to conventional autopsy? Infection of human lymphomononuclear cells by SARS-CoV-2. bioRxiv European Respiratory Society: standards for quantitative assessment of lung structure SARS-CoV-2 triggered neutrophil extracellular traps (NETs) mediate COVID-19 pathology. medRxiv Control CfD, Prevention. CDC 2019-novel coronavirus (2019-nCoV) real-time RT-PCR diagnostic panel Detection of 2019 novel coronavirus (2019-nCoV) by real-time RT-PCR. Euro surveillance : bulletin Europeen sur les maladies transmissibles = European communicable disease bulletin Pulmonary alveolar regeneration in adult COVID-19 patients. Cell research Histopathology and ultrastructural findings of fatal COVID-19 infections in Washington State: a case series Lung fibrosis: an undervalued finding in COVID-19 pathological series. The Lancet. Infectious diseases Neutrophil extracellular traps kill bacteria Respiratory Mechanics and Gas Exchange in COVID-19-associated Respiratory Failure The procedures followed in the study were approved by the National Ethics Committee -Brazil (CAAE: 32475220.5.0000.5440). The written informed consent was waived.