Follicular Mycosis Fungoides, a Distinct Disease Entity With or Without Associated Follicular Mucinosis

OBJECTIVE: To determine the clinicopathologic features and the disease course of patients with follicular mycosis fungoides (MF). DESIGN: A multicenter, 14-year, retrospective cohort analysis. SETTING: Dutch Cutaneous Lymphoma Group. PATIENTS: Fifty-one patients with the clinicopathologic features of follicular MF with (n = 49) or without (n = 2) associated follicular mucinosis. Follow-up data were compared with those of 158 patients with the classic epidermotropic type of MF, including 122 patients with generalized plaque-stage MF (T2 N0 M0) and 36 patients with tumor-stage MF (T3 N0 M0). OBSERVATIONS: Characteristic clinical features not or rarely observed in classic MF were the preferential localization of the skin lesions in the head and neck region (45 of 51 patients), the presence of follicular papules, alopecia, acneiform lesions, mucinorrhoea, and often severe pruritus. Characteristic histologic findings were the presence of perifollicular neoplastic infiltrates with a variable degree of folliculotropism, but generally no epidermotropism, follicular mucinosis (49 of 51 cases), and often a considerable admixture of eosinophils and plasma cells. Response on initial treatment, risk of disease progression (development of extracutaneous disease and/or death from lymphoma), and disease-specific and overall survival of patients with follicular MF were worse than in classic MF patients. The actuarial disease-specific survival was 68% at 5 years and 26% at 10 years. CONCLUSIONS: Follicular MF shows distinctive clinicopathologic features, is more refractory to treatment, and has a worse prognosis than the classic type of MF; it should be considered a distinct type of cutaneous T-cell lymphoma. Based on these results and those of other studies, we suggest the term follicular MF for cases with or without associated follicular mucinosis.