Summary

A 60-year-old African-American male patient with a history of seizures, developmental delay, long history of behavioural issues with psychotic episodes, heart, liver, thyroid and kidney diseases presented for evaluation of a right neck skin lesion. Physical examination revealed a shiny purplish-red plaque on the right neck and a thin pink plaque on the posterior neck. The lesions were similar in appearance, but different enough to warrant skin biopsy of each. Pathology demonstrated mycosis fungoides (MF) on the right neck and dermatofibrosarcoma protuberans (DFSP) on the posterior neck. The identification of two rare conditions made us reconsider our diagnosis. After further review, the right neck skin lesion was thought to be anticonvulsant-induced cutaneous lymphoid hyperplasia, not MF. This case demonstrates how insufficient skin biopsy can have significant clinical consequences. Biopsy of the right neck only would have overlooked a DFSP and incorrectly given the patient a diagnosis of MF.