Cytologic and histologic features of COVID-19 post-vaccination lymphadenopathy.

In this study, we present six cases of axillary or supraclavicular lymphadenopathies in the days following to the Pfizer-BioNTech vaccine's first dose and its study for fine-needle aspiration cytology (two patients), biopsy with a gross needle (two patients), and the evolution of two other patients. Cytological smears and histological sections reveal reactive nodes, predominantly T, CD8, and the presence of atypia with striking mitosis. Differential diagnosis with viral lymphadenopathies and lymphoma is important, so the clinical correlation, in a vaccination context, sudden appearance, and progressive decrease in days of the adenopathy, is essential. In this article, we have studied the cytohistological manifestations of post-Pfizer-BioNTech vaccination lymphadenopathy and discussed its differential diagnosis.