Follicular Mycosis Fungoides: Variability of a Rare Entity

Skinmed. 2005;4(1):12-17. 

In This Article

Abstract and Introduction

Objective: Three patients with follicular mycosis fungoides (FMF), a rare variant of folliculotropic cutaneous T-cell lymphoma, are discussed. Follicular involvement in cutaneous T-cell lymphoma commonly presents clinically with alopecia, follicular cysts, or comedo-like lesions usually associated with follicular mucinosis and strong epidermotropism. In contrast, FMF, in a strict sense, has been defined as a lymphocytic infiltration of hair follicles in the absence of both epidermal invasion and follicular mucin.
Discussion: Case 1 shows a clinically stable form of FMF characterized by circumscribed alopecia and its persistent resistance to topical therapeutic approaches. In contrast, Cases 2 and 3 demonstrate that classic mycosis fungoides lesions and FMF can occur simultaneously and that transitions occur from mycosis fungoides to FMF and vice versa. These observations strengthen the concept that FMF and mycosis fungoides represent just two variants of one entity of cutaneous T-cell lymphoma. In Case 3, rapid progression into tumor-stage mycosis fungoides and the follicular infiltration was controlled with bexarotene.
Conclusions: Because it was previously suggested that FMF may have a worse prognosis compared with classic mycosis fungoides, this impressive response to bexarotene is of great clinical interest and may spark new studies employing this novel retinoid for FMF treatment.

Mycosis fungoides (MF) is the most common form of cutaneous T-cell lymphoma (CTCL).[1] It is a malignancy of CD4+ helper T lymphocytes that initially involves the skin and may later encompass other parts of the organism.[2] Early observations showed that MF may also present with infiltrated follicular papules, cysts, or comedo-like lesions.[3] Commonly, such follicular involvement in MF is histologically characterized by follicular mucinosis.[3] In contrast, a very rare clinical and histologic variant of the disease is pilotropic or follicular MF (FMF).[4] In a strict sense, in FMF the presence of follicular lesions is not associated with follicular mucinosis but results from pure infiltration of the hair follicles by lymphoma cells (positive pilotropism, folliculotropism).[4] Thus, the histologic presentation of FMF clearly differs from classic MF, with follicular involvement presenting with epidermotropism and mucin deposits as main characteristics.

In this report, we describe three patients with FMF in the strict sense who show the variability of this rare entity; however, the concept of FMF as an entity of its own is challenged by the fact that transitions between common MF and FMF can occur in both directions and simultaneous occurrence is also possible. In at least one of our patients, FMF marked the onset of an aggressive course, which supports previous assumptions that FMF may sometimes have a particularly poor prognosis. Since we effectively treated this patient with bexarotene, after failure of chemotherapy (chlorambucil), this new treatment option needs further consideration in this particular variant of CTCL.

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