Atypical follicular hyperplasia with light chain-restricted germinal centers after COVID-19 booster: a diagnostic pitfall.

There has been a surge in COVID-19 vaccine-associated lymphadenopathy (LAD), including after the booster dose of vaccine. This can create diagnostic dilemmas in oncology patients as the relatively sudden LAD can mimic metastasis or cancer recurrence, at a risk of leading to additional but unnecessary anti-neoplastic therapy. Here we report the histopathologic features in a case of persistent LAD occurring in a patient with history of breast invasive ductal carcinoma which followed a COVID-19 vaccine booster. A needle core and then excisional biopsy showed atypical follicular hyperplasia with features that histologically and phenotypically could mimic follicular lymphoma, but the findings were ultimately interpreted to be reactive in nature and related temporally to COVID-19 vaccine. To our knowledge, this is the first case of an atypical lymphoproliferative lesion with features potentially mimicking lymphoma associated with COVID-19 vaccine.