Track: Case Reports

Abstract:

Intravascular large B-cell lymphoma (IVLBCL) is a rare, aggressive subtype of extranodal diffuse large B-cell lymphoma. Pathologically, it is defined by neoplastic B-lymphocytes proliferating within small-to-medium-sized-blood vessels, causing microvascular occlusion and subsequent organ-dysfunction. IVLBCL is categorized into three distinct clinical variants: classic, hemophagocytic-syndrome-associated, and a cutaneous form. IVLBCL is a pertinent differential diagnosis among intravascular reactive and neoplastic processes.

We present a case of an 86-year-old male who presented with a five-week history of rapidly progressing, violaceous, non-blanchable patches and thin plaques on his bilateral inner thighs, accompanied by mild pruritus. His past medical history was significant for prostate cancer status post-radiation therapy. A punch-biopsy was performed with a clinical differential diagnosis including angiosarcoma, Kaposi sarcoma, and B-cell-lymphoma. Histologically, the biopsy revealed numerous enlarged lymphocytes within small vessels throughout the dermis and subcutis. The atypical lymphocytes stained positive for CD20, BCL-2, BCL-6, MUM-, and CD5, confirming diagnosis of IVLBCL.

The patient was referred to oncology to rule out systemic disease. A PET scan was performed, which revealed localized FDG-avid subcutaneous thickening without generalized lymphadenopathy or distant metastasis. The patient was treated with R-CHOP and intrathecal methotrexate. Follow-up imaging showed no new lesions, and multiple cerebrospinal fluid analyses were negative for a B-cell lymphoproliferative process, ruling out central-nervous-system involvement.

This case highlights the need for a broad differential diagnosis of intravascular processes. Beyond well-known vascular neoplasms like angiosarcoma and Kaposi sarcoma, and reactive conditions like intravascular histiocytosis and intravascular papillary endothelial hyperplasia, the differential must also include rare entities such as IVLBCL.

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