Abstract: A 50-year-old male presented with an erythema on the right chest for more than 20 years. Histopathological examination showed hyperkeratosis, acanthosis, a papillary dermal lymphocytic infiltrate with prominent epidermotropism by atypical lymphocytes. Immunohistochemical investigation showed that the lymphocytes were positive for CD3, CD4, CD5, CD7, CD8, and negtive for CD20. The clonal gene rearrangement test for T lymphoma was positive. The diagnosis of mycosis fungoides was made. The patient was treated with 0.05% desonide cream for 4 weeks, with good response.

Key words: unilesional, mycosis fungoides