Background: Follicular mycosis fungoides (FMF) is a recently described variant of cutaneous T-cell lymphoma, histopathologically characterized by infiltrates of atypical CD4 ⁺ T lymphocytes around and within the epithelium of the hair follicles (folliculotropism). To date, only four cases of FMF have been reported.

Objective: Our goal was to identify cases of FMF and compare them with those previously reported.

Methods: The clinical and histopathologic features of three cases of FMF were analyzed. In addition, in one case immunohistochemical analysis in paraffin-embedded and frozen tissue as well as genotypic studies were performed.

Results: The three reported cases showed typical histologic findings of FMF, namely, perifollicular and intrafollicular infiltrates of atypical lymphocytes, in the absence of either epidermotropism or follicular mucinosis. Clinically, the lesions were similar to classic MF, but also contained follicular papules. Immunohistochemistry and gene rearrangement studies showed findings similar to classic MF.

Conclusion: FMF is a rare variant of cutaneous T-cell lymphoma. Including our three cases, only seven patients have been reported. We hypothesize that the follicular epithelium in patients with FMF may express increased levels of skin-selective homing receptors and adhesion molecules. These may be involved in the induction of the folliculotropism of atypical lymphocytes. (J Am Acad Dermatol 1997;36:563-8.)