Cutaneous T‐cell lymphoma occurring with a melanocytic proliferation, masquerading as a nonhealing ulcer with reactive changes

Two of the most challenging areas in dermatopathology are lymphoproliferative disorders and melanocytic lesions. We present a case of peripheral T‐cell lymphoma occurring with an intradermal melanocytic proliferation. A 63‐year‐old Caucasian man presented with a 12‐cm edematous, erythematous to violaceous, scalp ulceration that had enlarged over six months. Previous biopsies showed reactive changes which were concerning for infection. The last biopsies showed small to intermediate sized, angulated cells with clear cytoplasm within the dermis, with extension into the epidermis. These cells stained positive with markers for CD3, CD45RO and CD43, yet showed decreased expression of pan‐T‐cell markers CD5 and CD7, and absent expression of CD4, CD8, CD56 and CD57 and EBV. Molecular studies showed a clonal T‐cell receptor gamma chain gene rearrangement. The diagnosis was peripheral T‐cell lymphoma, unspecified. Another biopsy from an indurated area separate from the ulcer showed scattered, enlarged cells embedded in the same lymphocytic infiltrate. No mitotic figures were identified. These cells stained for S100 and Melan‐A, in a partly nested arrangement. This was felt to represent a melanocytic nevus. This case likely represents an extraordinary coincidence of two distinctly different neoplasms.

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