Abstract

Epidermotropism is most commonly seen in cutaneous T-cell lymphoma, mycosis fungoides type; but can also be seen in a wide variety of other T-cell lymphomas, and remains rarely reported in B-cell lymphomas (e.g., epidermotropic cutaneous marginal zone B-cell lymphoma). Here we report a case of epidermotropic diffuse large B-cell lymphoma, leg type with marked epidermotropism. An 88-year-female with a past medical history of hypertension, stroke, and DCIS in bilateral breasts in remission presented with an erythematous rash accompanied with a burning sensation on her bilateral lower legs that had been present for three months. The rash progressively spread to the buttocks, back, creases, and abdomen. Triamcinolone provided mild relief, but the rash became more raised and developed nodules. She possessed no constitutional symptoms. A punch biopsy from the back showed an atypical infiltrate in the superficial dermis in a band-like distribution with epidermotropism. The infiltrate was composed of large cells with scattered smaller cells in the background. The large cells display epidermotropism, pleomorphism, mitotic figures, and prominent central nucleoli (i.e., immunoblasts). Immunohistochemically, the atypical cells showed immunoreactivity for CD20, CD79a, focally for BCL-2, and BCL-6, and strong expression of MUM-1 in the majority of the cells. Ki-67 had a high proliferation index (50% in the hot spots). CD3 highlighted a background of T-cells that were positive for CD4 and CD8 (small-sized lymphocytes). PCR was positive for heavy chain gene rearrangement. Imaging showed no evidence for systemic involvement. The final diagnosis was primary cutaneous diffuse large B-cell lymphoma, leg type. This case highlights that diffuse large B-cell lymphoma can show prominent epidermotropism mimicking a T-cell process on histomorphologic basis. Further studies are needed to determine if this has any significance on prognosis or relates to early detection of the disease.

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