Florid lambda-monotypic B-cell proliferation in fatal severe fever with thrombocytopenia syndrome virus infection-associated necrotizing lymphadenitis: a potential diagnostic pitfall

초록

Severe fever with thrombocytopenia syndrome (SFTS) is a severe systemic inflammatory response syndrome caused by a potentially lethal tick-borne SFTS virus. A rapid and robust extrafollicular B-cell response to fatal or sublethal SFTS virus infection is known to generate a robust extrafollicular B-cell response that is skewed to lambda-monotypic B-blasts. We present a case of fatal SFTS virus infection-associated histiocytic necrotizing lymphadenitis showing an effaced nodal architecture due to florid lambda-monotypic B-blasts that can raise a diagnostic pitfall in hematopathology. We examined histologic and immunophenotypic features of inguinal lymph node tissue of a 49-year-old Korean woman, who presented with a high fever and painful left inguinal lymphadenopathy associated with fatal SFTS virus infection. The nodal architecture of the excised lymph node appeared to be diffusely effaced by expanded paracortical zones by an extensive proliferation of immunoblast-like large lymphoid cells along with minor foci of necrosis associated with infiltration of phagocytosing histiocytes, featuring the proliferative phase of Kikuchi-Fujimoto disease. Immunophenotypically, however, the proliferating cells consisted predominantly of lambda-monotypic B-blasts. This misleading aberrant B-cell response should be recognized by pathologists to avoid misinterpretation of the lambda-monotypic B-blast proliferation in SFTS viral infection-associated histiocytic necrotizing lymphadenitis as diffuse large B-cell lymphoma.

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