ABSTRACT
BACKGROUND: Folliculotropic mycosis fungoides (FMF) represents a variant of MF characterized by hair follicle invasion of mature, CD4-positive small lymphoid cells with cerebriform nuclei. The disease displays resistance to standard treatment modalities and has an unfavourable course. OBJECTIVE: Clinical analysis of 17 patients with FMF collected between 2005 and 2012, investigation of tumour cells and involved hair follicle. METHODS: Re-evaluation of clinical data, wide panel immunohistochemistry investigation on paraffin-embedded biopsy material, T-cell receptor gene rearrangement analysis of the samples. RESULTS: Male and older age group predominance, frequent head-neck involvement, acneiform lesions, keratotic plugs, cysts, nodules, follicular papules, alopecia and classic mycosis fungoides-like plaques represented the main clinical characteristics. Treatment response showed a wide range from transient complete response to therapy resistance and death due to the disease. The pathological alterations: folliculotropism, mild epidermotropism, follicular plugging, mucinous degeneration of hair follicle, basaloid hyperplasia, syringotropism were similar to those observed previously. The first case of a CD8-positive folliculotropic mycosis fungoides - with unusual clinical presentation - is reported here. Nestin overexpression of mesenchymal cells of the isthmic and suprabulbar regions of hair follicle and the reappearance of dermal nestin-expressing cells were observed in association with immature dendritic cell hyperplasia. Altered CK19 expression was detected suggesting a potential role of follicular keratinocytes in the disease process. It was found that a proportion of neoplastic T cells constantly express programmed death-1 receptor in our patients contrary to classic mycosis fungoides. CONCLUSION: The spectrum of the clinical manifestation and the course of folliculotropic mycosis fungoides are broad and differ from classic mycosis fungoides. Folliculotropic neoplastic T-cell proliferation is associated with activation of inflammatory reactive T- and B-lymphoid cells, mesenchymal cells and changes in the hair follicle.
