CD4/CD8 dual-positive mycosis fungoides: a previously unrecognized variant

Mycosis fungoides (MF) is a primary cutaneous lymphoma characterized by atypical T-lymphocytes that usually presents as patches and plaques on photoprotected areas of the body, such as the groin and buttocks. Classically, the atypical lymphocytes in MF are CD3/CD4 positive with loss of CD7 and less often loss of CD5. In a minority of cases, the atypical infiltrate is CD8 positive. We report a case of biopsy-proven MF in an elderly woman who presented with sclerodermoid lesions on her abdomen and thigh. Immunohistochemical studies revealed coexpression of CD4 and CD8 in a subset of atypical T-lymphocytes, and this was confirmed with flow cytometry. To our knowledge, this is the first report of a CD4/CD8 dual-positive MF.