Mycosis fungoides associated with unusual epidermal hyperplasia.

A 58-year-old white woman presented with widespread pruritic brownish plaques and hyperpigmented flexural lesions with a velvety appearance. On histopathological examination, the macules were diagnostic of mycosis fungoides, plaque stage, and the flexural lesions showed epidermal hyperplasia with a seborrhoeic keratosis-like appearance. There was intense mucin deposition and marked reduction of elastic fibres in the papillary dermis, as well as a moderately dense dermal lymphoid infiltrate composed of CD4+ T cells with occasional atypia and focal epidermotropism. The clinical and pathological manifestations of cutaneous T-cell lymphomas, including mycosis fungoides (MF), may show considerable variation. Apart from the three classic stages, a number of unusual clinical presentations and a broad spectrum of histopathological findings have been reported in the literature. In this report, a case of MF, plaque stage, with flexural lesions clinically reminiscent of (pseudo)acanthosis nigricans is presented. On histopathological examination, there was epidermal hyperplasia with a seborrhoeic keratosis-like appearance, with intense deposition of mucin and marked reduction of elastic fibres in the papillary dermis, together with a lymphoid infiltrate composed mainly of CD4+ cells with occasional atypia and epidermotropism. Cytokines produced by the lymphocytes in the infiltrate might account for the epithelial and dermal changes that characterize this peculiar variant of MF.