Follicular malignant melanoma: primary follicular or folliculotropic?

Follicular malignant melanoma (FMM) is a rare variant of melanoma arising on sun-damaged skin of elderly patients. It is characterized histopathologically by a prominent involvement of 1 or 2 adjacent hair follicles. The authors report 3 new cases of FMM (M:F = 2:1; age range, 23-67 years; median age, 50 years) located on the scalp, cheek, and upper back. Complete effacement of the hair follicle, replaced by neoplastic melanocytes, was observed in 1 case. The interfollicular epidermis and adventitial dermis were involved in all 3 cases. Our series shows that FMM is not restricted to elderly patients but may arise also in young individuals without association with chronic sun damage. FMM should be distinguished from folliculotropic metastases of melanoma and from atypical melanocytic nevi. Although the histopathological features and the term FMM may suggest a derivation from melanocytes of the hair follicle, the exact origin of neoplastic cells is yet unclear, and at least some of these cases may represent folliculotropic examples of primary epidermal malignant melanoma.