Herpes folliculitis masquerading as cutaneous lymphoma.

Herpes virus infections presenting as folliculitis are uncommon. We describe a 48-year-old white man with a distant history of a childhood gastric lymphoma and renal cell carcinoma presenting with an itchy eruption. He was concerned about recurrence. A punch biopsy revealed interface dermatitis with a dense atypical superficial and deep perivascular and periadnexal lymphohistiocytic infiltrate with occasional eosinophils extending to the subcutis, with destruction of vessel walls. It was composed of predominantly CD3-positive lymphocytes with scattered CD56-positive cells and CD20-positive cells, concerning for lymphoma. A T-cell gene rearrangement study was negative. Deeper sections uncovered multinucleated giant keratinocytes in the follicular epithelium of 1 hair follicle, consistent with herpes folliculitis. Cutaneous herpes infections can exhibit several variable clinical and histopathological features. Knowledge of alternative presentations of herpes infections, histological clues to the presence of herpes infections, and careful clinicopathological correlation are necessary to differentiate herpes infections from cutaneous lymphomas and other inflammatory dermatoses.