Track

Abstract

A 93-year-old man presented with a rapidly enlarging, painless mass of the right testis and a separate cutaneous lesion on the left ankle. There was no prior history of lymphoma or immunodeficiency. Clinical evaluation revealed no B-symptoms. Histopathologic examination of a shave biopsy from the left ankle revealed a diffuse, monotonous infiltrate of large atypical lymphocytes (centroblasts and immunoblasts) involving both upper and deep dermis, with prominent mitoses and apoptosis. Immunohistochemistry showed positivity for CD20, CD79a, BCL2, and partial BCL6; notably, CD10 was positive, an unusual finding in primary cutaneous DLBCL, leg type (PCDLBCL-LT). Separate examination of the right testis and spermatic cord revealed morphologically similar diffuse large B-cell lymphoma with a germinal center B-cell (GCB) immunophenotype (CD20+, CD79a+, BCL2 strongly positive, BCL6 weakly positive, CD10 weakly positive). Background T-cells and small B-cells were more prominent in the testicular lesion. The presentation of DLBCL in skin and testis with overlapping GCB immunophenotype poses a diagnostic challenge. While two primary extranodal lymphomas were ultimately diagnosed, the case brought forth an interesting differential considerations of two primary extranodal lymphomas versus secondary involvement or follicular lymphoma transformation. Aberrant CD10 positivity in PCDLBCL-LT, while uncommon, is documented and complicates classification.  Accurate diagnosis in multifocal extranodal DLBCL requires careful correlation of clinical features with pathology and immunophenotyping. Recognizing the aggressive nature and frequent CNS involvement of both primary testicular and cutaneous leg-type DLBCL underscores the importance of exhaustive systemic staging to inform prognosis and management.