Follicular Mycosis Fungoides Mimicking a Cutaneous B-Cell Lymphoproliferative Disorder

Follicular mycosis fungoides (MF) is a rare variant of MF characterized by atypical lymphocyte infiltrates around hair follicles. A reported case involved a patient with rapidly progressing follicular MF on the face and typical MF lesions elsewhere. Histology showed dense lymphoid infiltrates with folliculotropism and epidermotropism, and a prominent B-cell component, initially suggesting cutaneous B-cell lymphoma. The final diagnosis of follicular MF was confirmed by clonal T-cell receptor gene arrangements and absence of heavy chain gene rearrangements. This case highlighted the rapid progression of this MF variant and the diagnostic challenges due to its histological similarity to B-cell proliferative disorders.