ABSTRACT
Intravascular large B-cell lymphoma (IVLBCL) is a rare variant of diffuse large B-cell lymphoma, characterized by its unique morphology. Modern-day diagnostic methods like flow cytometry have limitations in accurate diagnosis of the disease making morphology the mainstay for its diagnosis and adequate management. Here, we present a case of IVLBCL with emphasis on diagnostic aids and adjuncts. A 63-year-old female presented with fever of unknown origin, seizers, hepatosplenomegaly, and peripheral cytopenias. Bone marrow aspirate shows a small number of atypical lymphoid cells. Flow cytometry done on the aspirate yielded 7% abnormal lymphoid cells; however, further, subclassification of this non-Hodgkin lymphoma was not aided by it. Bone marrow biopsy revealed the intrasinusoidal localization of the tumor cells, which were positive for CD20, BCL2, and Mum1 and along with flow cytometric expression of CD5 and lambda restriction of tumor cells; a diagnosis of IVLBCL was made. IVLBCL is a rare entity with protean clinical presentation which frequently leads to a delay in diagnosis. Modern diagnostic modalities like flow cytometry help in picking up even a small number of tumor cells; however, it is limited by failure to subcategorize the entity making morphology and immunohistochemistry as the backbone of its diagnostic workup.