Tricholemmoma: causes, symptoms, diagnosis, treatment

Trichilemmomas clinically resemble basalioma or seborrheic keratosis and are usually histological findings. The tumor is usually solitary, small in size, predominantly localized in the facial area, somewhat more often in men than in women, the average age of patients is 59 years. Multiple tumors are part of Cowden syndrome.

Pathomorphology of trichilemmomas. The tumor is lobular, located in the dermis. The tumor lobules consist of light, polygonal cells containing glycogen, surrounded on the periphery by darker ones, arranged in a palisade. Palisade-shaped tumor complexes are surrounded by a thick membrane, similar to the eosinophilic basement membrane. There is a tendency to keratinization. The tumor lobules are mostly located around hair follicles and grow in close proximity or in connection with the epidermis.

The flat variant of this tumor is characterized by less pronounced lobules that are located parallel to the epidermis.

Histogenesis of tricholemmoma. The peculiarity of tricholemmoma development is connected with cellular elements of differentiating tricholemmoma – the outer epithelial layer of the follicle. Specific type of keratin is formed in it, bypassing granular pre-stage, in the upper part of pilosebaceous complex of hair follicle – epidermoid type epithelium, i.e. keratinization occurs through keratohyalin stage. A.V. Ackerman (1993) takes completely different position with respect to tricholemmoma as an independent nosological form. From his point of view tricholemmoma is a viral wart in the reduction stage. According to the author, human papillomavirus can induce proliferation of epithelium of any part of pilosebaceous complex and sweat glands. With proliferation of the epithelium of the follicle funnel, the process takes the form of a follicular keratoma, and proliferation of the outer lining in the bulb area leads to the formation of complexes of light cells along the periphery of the bulb.