The diagnosis of early mycosis fungoides is often regarded as difficult or impossible due to the lack of clear-cut histopathologic criteria. Many authors have published observations of histologic features seen in biopsies of patients with mycosis fungoides and have offered parameters that may be helpful in diagnosis. In the study, undertaken by members of the EORTC Cutaneous Lymphoma Study Group, the proposed histologic features are tested for sensitivity and specificity. This commentary discusses some of the historical issues and the value of the EORTC study pertaining to the diagnosis of early mycosis fungoides.