DEAR EDITOR, A 46-year-old Japanese man had experienced multiple slightly scaly erythematous patches on his flanks, hips and thighs for about 20 years, and had received no medical treatment. The patient noticed a small red nodule on the posterior aspect of his right thigh, which increased in size and ulcerated rapidly over the course of 1 year. The tumour was 4 cm in diameter, forming a central ulcer with yellow and black necrotic tissue ( Fig. 1a,b). A biopsy specimen taken from an erythematous patch showed atypical T-cell infiltration with epidermotropism and multiple Pautrier microabscesses ( Fig. 2a). These cells were positive for CD3 and CD4, but not for CD8 or CD30 ( Fig. 2b-d, and data not shown). The condition was diagnosed as mycosis fungoides (MF).A biopsy specimen taken from the tumour revealed dense infiltration of highly atypical medium-sized lymphocytes in the dermis (Fig. 2e). Pleomorphism and mitotic figures were observed (Fig. 2f). Immunohistochemically, atypical lymphocytes were positive for CD3, CD8 and granzyme B, but not for CD4 or CD30 (Fig. 2g,h, and data not shown). T-cell receptor (TCR) gene rearrangement analysis using polymerase chain reaction (PCR) revealed monoclonal peaks of the same size for the b and c chains of TCR in both lesions (Fig. 2i, j). The tumour was removed surgically. Erythematous lesions were treated with a topical steroid and narrowband ultraviolet B phototherapy. No new nodules or tumours developed for 31 months after the initial diagnosis.

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