Histologic mimickers of mycosis fungoides: a review

Mycosis fungoides (MF) is a rare type of non-Hodgkin's lymphoma affecting the skin. Because MF develops slowly over several years and may have a variety of clinical presentations, including itchy patches, plaques or tumors that may be confused with common benign conditions such as eczema and psoriasis, the disease presents a diagnostic challenge. The average time to diagnosis varies but is frequently as long as 3 to 6 years. Skin biopsies frequently reveal non-specific features of several dermatoses; thus, histologic evaluation of the disease is also challenging. Importantly, various significant and/or benign conditions may mimic MF histologically and result in a misdiagnosis of MF. Here we review the reported histologic mimickers of MF and discuss both similar and differentiating features of each, in order to aid in more accurate interpretation of diagnostically challenging skin biopsies. Clinicopathologic correlation is ultimately essential to make accurate diagnosis of MF and its histologic mimickers.