Trichofolliculoma: causes, symptoms, diagnosis, treatment

Trichofolliculoma is quite rare, usually not clinically recognized and most often is a histological finding. The age of patients ranges from 11 to 77 years (average 47 years), with a slight predominance of women. Trichofolliculoma is most often localized on the skin of the nose or perinasally in the form of a solitary papule or small nodule with a diameter of 0.4-0.6 cm, hemispherical in shape with a smooth surface and a clearly distinguishable wide pore, in the center of which there is sometimes a tuft of thin, colorless hairs.

Pathomorphology of trichofolliculoma. Trichofolliculoma may be of different sizes and is located in the dermis and, in some cases, in the subcutaneous adipose tissue. The apex of the formation is in the form of one or several cystically dilated, sometimes curved, open outward funnels of the hair follicle. The funnels are usually filled with oral masses. Cell cords extend radially from the epithelial lining of the funnel, forming second-order follicular structures. They may contain cystically dilated cavities filled with horny masses. In addition to vellus follicles connected with the epithelium of the main funnel, single or grouped immature vellus follicles may be located separately. Complexes resembling embryonic follicular rudiments may bud off from the latter. Around each follicular complex extending from the central funnel, there is a clearly distinguishable connective tissue capsule. In a tangential section, follicular structures can be completely enclosed in such a membrane. Among such growths, there are individual horn cysts, as well as complexes of small cells with intensely stained nuclei. In the cells of some follicles, despite the absence of vacuolization, a large amount of glycogen is noted. A.K. Apatenko (1973) considers trichofolliculoma as an intermediate condition between a developmental defect of hair follicles and trichoepithelioma and considers it a highly differentiated variant of the latter.

Differential diagnosis is based on the presence of immature follicular structures, which distinguish this tumor from a hairy nevus. In trichoepithelioma, there is an organoid structure of the hair matrix.