Folliculotropic and syringotropic mycosis fungoides mimicking basal cell carcinoma.

Mycosis fungoides (MF) is characterized by a clonal proliferation of skin-homing mature T cells with special predilection for involving the epidermis. Folliculotropic and syringotropic MF typically present with erythematous papules, patches, and plaques, with punctate accentuation that is folliculocentric in the former. We report a 67-year-old woman, with an extensive history of allergic contact dermatitis, who was referred to the Mohs surgery clinic with a large pink plaque extending from the nasal bridge to the right upper medial cheek concerning for basal cell carcinoma. An outside punch biopsy showed benign basaloid follicular neoplasm. The patient was found to also have indurated erythematous plaques of the bilateral upper arms and erythematous scaly patches of bilateral arms and legs, abdomen, lateral trunk, buttocks, and groin. Owing to concern for possible cutaneous lymphoma, punch biopsies were performed which revealed the diagnosis of folliculotropic and syringotropic MF. Of note, folliculotropic and syringotropic MF are often, but not uniformly, characterized by a more aggressive disease course. This case highlights the importance of a high index of suspicion and awareness of all clinical and histopathologic pitfalls to avoid misdiagnosis of MF.