Small Cell Variant of Intravascular Large B-Cell Lymphoma: Highlighting a Potentially Fatal and Easily Missed Diagnosis

CONTEXT: Intravascular large B-cell lymphoma (IVLBCL) is a rare non-Hodgkin B-cell lymphoma with a poor prognosis. While typically described as comprising large atypical cells restricted to the lumina of small blood vessels, it can show variability in cell size. OBJECTIVE: To report the clinicopathologic features of the IVLBCL with small cell morphology and discuss the practical implications of our findings. DESIGN: We searched our archives for all IVLBCL diagnosed in our institution for the last 25 years (1992–2017). Slides were reviewed independently by two hematopathologists. RESULTS: We found a total of 11 cases of IVLBCL. Bone marrow, brain, lymph node, pericardium, small bowel, and fallopian tube and ovary were the organs in which the lymphoma was initially diagnosed. One of the cases initially diagnosed in the marrow showed intrasinusoidal involvement by a small cell lymphoma; the diagnosis was confirmed by random skin biopsies showing intravascular large cells with the same phenotype. Retrospective review of the liver on this case also showed the intrasinusoidal involvement by the disease consisting of small cells. In another case, IVLBCL that was initially diagnosed in a small bowel biopsy was retrospectively found in a breast biopsy, but with small cell morphology. CONCLUSIONS: Our findings suggest that, in the presence of high clinical suspicion, IVLBCL should be high in the differential diagnosis when lymphoma is predominantly intravascular, even when the tumor cells are small. A timely diagnosis of this entity can be critical. Hence, awareness of a small cell variant of IVLBCL should be increased.