Inverting follicular keratosis (follicular keratoma): causes, symptoms, diagnosis, treatment

The first description of the tumor of inverting follicular keratosis (follicular keratoma) was made by Helwig in 1954. Since then, disputes about the eligibility of this new growth to form an independent nosological form have not ceased. A. Mehregan (1983), JM Mascaro (1983) are supporters of unconditional follicular genesis and recognize follicular keratoma as an independent nosological unit.

W. Lever, G. Schaumburg-Lever (1987), W. Ackerman (1992) consider follicular keratoma as a variant of a simple or seborrheic wart. JT Headington (1983), HZ Lund (1983) are of the opinion that the nosological affiliation of the tumor remains uncertain.

Neoplasm can occur at any age, however, according to B. Ackerman (1992), in 80% of cases the process develops in persons older than 50 years. Several tumors occur in men. The predominant localization is the skin of the face and scalp. It is a small painless nodule with a diameter of up to 1 cm, grayish color, usually with hyperkeratosis. It is not clinically identified, and most often patients are referred to a pathomorphological examination with a diagnosis of vulgar or seborrheic warts, keratopapillomas, and less often basalomas (in case of ulceration).

Pathomorphology of inverting follicular keratosis (follicular keratoma). Microscopically, the tumor is represented by wide, irregular outlines of acanthotic growths of flat-epithelial cells of varying degrees of differentiation. Among them there are small elongated, basaloid-type cells with hyperchromic nuclei, as well as large cells of prickly type with a light nucleus. A clear nucleolus, a wide rim of the enlightened cytoplasm and pronounced intercellular bridges. Between these two types there are various transitional forms, which causes a certain cellular and structural polymorphism. Basaloid elements are grouped mainly along the periphery of the complexes. In the follicular keratome diffuse and focal keratinization is characteristic, characteristic for the funnel of the hair follicle and interfollicular epidermis. No less characteristic feature is small-focal keratinization in the form of "eddies" - usually small basal or rounded clusters of concentrically grouped epithelial cells that flatten towards the center and contain keratin. For the follicular keratoma is also characteristic of the presence of horny cysts of fairly large sizes, sometimes of irregular configuration, as well as foci of dyskeratosis. Ultrastructurally, "twist" cells have signs of incomplete keratinization - the intercellular desmosomal contacts are small, shortened, and located at a considerable distance from each other. The bundles of tonofillments are shortened, and in the cells of the neutral sections of the formation, bundles of tonofilaments are marked without any definite orientation. In the stroma around the tumor growths, inflammatory infiltrates of lymphohistiocyte character are detected.

Histogenetically, the tumor is associated with the epithelium of the funnel of the hair follicle.

Differentiate the tumor from vulgar and seborrheic warts, keratopapilloma, squamous cell carcinoma, kerato-acanthoma, eccrine powder. In the center of squamous cell cancer, atypia and polymorphism are detected, in keratoacanthoma and eccrine pore there is no piloid differentiation, and in addition, in the eccrine pore there are flow structures sometimes filled with homogeneous masses.

[1], [2], [3], [4], [5]