Defining the mimics and clinico-histological diagnosis criteria for mycosis fungoides to minimize misdiagnosis☆☆☆

BACKGROUND Mycosis fungoides (MF) is a significant diagnostic challenge; it has various differential diagnosis especially at an early stage. Our aim was to describe mimics of MF clinically and histologically, and to define significant diagnostic criteria of the disease. METHODS This was a retro-prospective cohort of 370 patients in whom the diagnosis of MF was suspected clinically. RESULTS MF was histologically confirmed in 15.4% of cases and rejected in 84.5%. Other identified histologically diagnosis were eczema, psoriasis; nonspecific dermatitis, lichen, lupus; pseudolymphoma, parapsoriasis and toxidermia. 4 patients with palmoplantar MF were wrongly treated as eczema, and 10 patients with psoriasiform MF were initially treated as psoriasis. We also described the clinical, histological and immunohistochemistry diagnostic criteria for distinguishing MF from benign dermatosis. CONCLUSIONS Misdiagnosis of MF was a real problem for this study, because it shared common clinical and histological characteristics with other inflammatory diseases like eczema and psoriasis. Therefore, defining significant clinico-histological diagnosis criteria of MF would be of great help and would increase the accuracy of the diagnosis.