Follicular mycosis fungoides: Clinicohistopathologic features and outcomes in a series of 12 Chinese cases.

Background Follicular mycosis fungoides is a distinct variant of mycosis fungoides with a broad clinical spectrum. Recently, many studies have indicated that follicular mycosis fungoides should be divided into different subtypes with disparate prognoses. Objective To define the clinicohistopathologic features and outcomes of follicular mycosis fungoides and to identify risk factors that may be related to the prognosis of Chinese patients with follicular mycosis fungoides. Materials and methods We conducted a single-centre retrospective study and reviewed the clinical, histopathologic and immunophenotypic data of 12 patients diagnosed with follicular mycosis fungoides between 2009 and 2020 in the Department of Dermatology of West China Hospital of Sichuan university. Results A total of 12 patients (seven males and five females) with a mean age of 30 ± 14 years (age range 16-55 years) were included. Scalp and face were the most common involved sites (100%). Follicular papules, acneiform lesions, plaques, and nodules, were the main clinical presentations. Histopathological findings were consistent with the classic manifestations of follicular mycosis fungoides, including folliculotropism, perifollicular and intrafollicular lymphocytic infiltrates and mucinous degeneration. Interferon α-1b was the most common treatment. Four patients died of follicular mycosis fungoides in three years. Notably, immunohistochemical analysis revealed a decreased number of CD20+ cells in the deceased patients. Limitations This is a retrospective evaluation with a small number of cases; further prospective studies are warranted to support our inferences. Conclusion Our patients were much younger than in previous studies. The observed difference in this cohort may be explained by race, in addition to the limited number of cases. A decreased number of B cells might be associated with a poor prognosis, and more studies are necessary to discover the role of B cells in follicular mycosis fungoides as well as in mycosis fungoides.