key: cord-0912348-0taij1tc authors: Tan, Nicholas Jin Hong; Tay, Kai Xun Joshua; Wong, Soon Boon Justin; Nga, Min En title: COVID‐19 post‐vaccination lymphadenopathy: Report of cytological findings from fine needle aspiration biopsy date: 2021-08-25 journal: Diagn Cytopathol DOI: 10.1002/dc.24863 sha: 7e45745be5041384d826003b51b1d75c404d2705 doc_id: 912348 cord_uid: 0taij1tc The coronavirus COVID‐19 pandemic has spurred the rapid development of vaccines, with vaccination programmes already underway in many countries. Regional lymphadenopathy is one of the documented side effects of vaccination. We document the fine needle aspiration cytological findings of an enlarged supraclavicular lymph node in a 34‐year‐old Asian female following the first dose of the Pfizer‐BioNTech COVID‐19 mRNA vaccine, which appears to be the first such report in a premorbidly well patient with no known history of malignancy. The cytological findings featured a reactive pattern in keeping with follicular hyperplasia, with prominent germinal centre elements including lymphohistiocytic aggregates and tingible‐body macrophages. Despite an increased proportion of larger lymphocytes, the overall pattern was in keeping with a reactive pattern, bearing in mind the temporal and geographic relation to the vaccination injection. In instances of localised lymphadenopathy, particularly in supraclavicular or axillary locations, pathologists should be cognizant of the possibility of post‐vaccination reactive lymphadenopathy, and seek clinical and radiological hints favouring a benign process, whilst recognising potential morphological overlaps with lymphoproliferative disorders. Awareness of this diagnostic pitfall is especially important as COVID‐19 vaccination coverage is ramped up worldwide, leading to an expected increase in incidence of post‐vaccination reactive lymphadenopathy. The COVID-19 pandemic has spurred the rapid development of several vaccines over the last year. In Singapore, vaccination using the Pfizer-BioNTech COVID-19 mRNA vaccine is currently underway. One of the documented side effects of the Pfizer-BioNTech COVID-19 vaccine is post-vaccination lymphadenopathy. 1 We report findings of a lymph node aspirate from a 34-year-old Asian female patient who experienced left supraclavicular lymphadenopathy On palpation, there was a slightly tender, ovoid left supraclavicular lymph node measuring 10 mm in maximal dimension. Examination of the ear, nose and throat, including nasopharyngeal endoscopy, was unremarkable. At a follow-up visit 8 days later (24 days post-vaccination), the lymphadenopathy persisted but was no longer tender. Bedside ultrasound revealed a well-circumscribed lymph node measuring 10.9 Â 9.9 Â 7.1 mm with minimal internal vascularity and no calcification. The hilum was not clearly visualised, however, no sonographically suspicious features were noted. In view of persistent supraclavicular lymphadenopathy in the context of an otherwise unremarkable head and neck examination, a fine needle aspiration (FNA) biopsy was performed to exclude an occult metastatic malignancy from thoracic and abdominal sites. Direct airdried and alcohol-fixed smears of the aspirate were stained with Hemacolor and Pap stains respectively. The smears revealed a mixed lymphoid population comprising a range of small to large lymphocytes. There was an increased proportion of large, activated lymphocytes in some areas ( Figure 1A ). The larger lymphoid cells featured a thin rim of bluish cytoplasm, and small, sometimes peripheral nucleoli. Germinal centre components including lymphohistiocytic aggregates with follicular dendritic cells, tingible body macrophages and centroblasts were also present ( Figure 1B ). Tingible-body macrophages were particularly prominent and many contained abundant karyorrhectic debris ( Figure 1C , D). Plasma cells and eosinophils were not prominent. No necrosis or granulomas were seen. The overall findings favoured a reactive process that was suggestive of reactive follicular hyperplasia. No cellblock was processed and no ancillary studies were performed. Upon review a further 2 weeks later, the lymph node was observed to have reduced in size to 8.0 mm in maximal dimension. The patient subsequently proceeded with the second dose of vaccination. Four weeks following the second dose of vaccination (2 weeks after the first vaccination dose), she was seen in clinic where the lymph node was neither palpable nor readily appreciable on ultrasound. Post-vaccination lymphadenopathy refers to reactive changes occurring within lymph nodes following vaccination, and it has been documented in multiple vaccine types. 2 Finally, further studies to document different cytological patterns of reactive lymphadenopathy may also be relevant, in view of the variety of vaccines that are available in the market. Data sharing is not applicable to this article as no new data were created or analyzed in this study. Nicholas Jin Hong Tan https://orcid.org/0000-0001-7163-3233 Pfizer-BioNTech COVID-19 Vaccine EUA Fact Sheet for Recipients and Caregivers Development of unilateral cervical and supraclavicular lymphadenopathy after human papilloma virus vaccination Postvaccinial lymphadenitis. Hyperplasia of lymphoid tissue that simulates malignant lymphomas Lymphadenopathy in COVID-19 vaccine recipients: diagnostic dilemma in oncology patients COVID-19 mRNA vaccination-induced lymphadenopathy mimics lymphoma progression on FDG PET/CT Management of unilateral axillary lymphadenopathy detected on breast MRI in the era of coronavirus disease (COVID-19) vaccination Unilateral axillary adenopathy in the setting of COVID-19 vaccine Acute onset supraclavicular lymphadenopathy coinciding with intramuscular mRNA vaccination against COVID-19 may be related to vaccine injection technique Lymphadenopathy following COVID-19 vaccination: imaging findings review Lymphadenopathy associated with the COVID-19 vaccine COVID-19 vaccination and low cervical lymphadenopathy in the two week neck lump clinic -a follow up audit Unilateral axillary lymphadenopathy after coronavirus disease (COVID-19) vaccination COVID-19 vaccination-related lymphadenopathy: what to be aware of Unilateral lymphadenopathy after COVID-19 vaccination: a practical management plan for radiologists across specialties Immune responses induced by mRNA vaccination in mice. Monkeys Humans Vaccines Efficient targeting and activation of antigen-presenting cells in vivo after modified mRNA vaccine administration in rhesus Macaques Axillary lymphadenopathy in a renal cell carcinoma patient after COVID-19 vaccination COVID-19 post-vaccination lymphadenopathy: Report of cytological findings from fine needle aspiration biopsy