Unilesional follicular mycosis fungoides: report of two cases with progression to tumor stage and review of the literature

Mycosis fungoides (MF) is the most common type of cutaneous lymphoma and has protean clinicopathological manifestations. Follicular or folliculotropic MF (FMF) is a rare variant, which histopathologically is characterized by pronounced folliculotropism of neoplastic T cells, with or without follicular mucinosis, and clinically by an impaired prognosis compared to classic MF. In contrast, unilesional MF is a very rare variant with an excellent prognosis, with a single case of large-cell transformation reported to date. The combination of folliculotropic and unilesional MF is very unusual, with only two cases reported to date. Here we report two patients with unilesional folliculotropic MF with progression to tumor stage in both patients. To the best of our knowledge, this is the first report on the disease evolution with large-cell transformation and progression of unilesional FMF. Complete remission was achieved by local radiation therapy in both patients. The differential diagnoses, classification and implications for the treatment of unilesional FMF as well as the pertinent literature are discussed.