Trichoepithelioma: causes, symptoms, diagnosis, treatment

Trichoepithelioma (synonyms: adeno-cystic epithelioma of Brooke, superficial trichoblastoma, trichoepithelioma nevus, etc.) represents the developmental defect of the hair follicle and sweat glands.

Causes and pathogenesis of trichoepithelioma. It is believed that trichoepithelioma develops from the area of the hair follicle with a large accumulation of Merkel cells at the place of attachment of the muscle lifting the hair. The disease is familial in 50-75% of cases and is inherited by an autosomal dominant type. Often found in women.

Symptoms of trichoepithelioma. Trichoepithelioma is often multiple, occurs mainly in young and adolescents, is mainly located on the face and body. Initially small-node tumor elements, whose diameter rarely exceeds 0.5 cm, arise on the skin of the nasolabial folds. Gradually, the number of nodules increases, they spread paranasally, capturing the skin of the nose, the scalp, the auricles, sometimes leading to occlusion of the external auditory canals, neck, and the interblade area. In many cases, a dominant craniocerephalic "epitheliosis" is expressed. Sometimes it is observed in combination with a cylinder, since there is a close histogenetic relationship between them. Frequent family cases, probably with autosomal dominant type inheritance.

Clinically distinguish between simple trichoepithelioma, which can be solitary and multiple, and desmoplastic.

Trichoepithelioma develops usually in childhood or later. There arise multiple small, usually 2-8 mm in diameter, dense tumor-like elements of hemispherical rounded outlines, the color of normal skin or light pink. Their surface is smooth, but in larger elements, telangiectasias are seen. Elements are localized primarily on the face (nasolabial folds, eyelids, upper lip, forehead), in the behind-the-ear region, on the scalp, less often in the interblade area. Elements can be arranged linearly or have a disseminated character.

Solitary trichoepithelioma in the main is located on the face, more often - in its central part. The tumor has the form of a papillomatous or fibropapillomatous outgrowth of a dense consistency of pink or flesh colored, up to 1 cm in size, with a network of dilated capillaries on the surface. The skin around the tumor is not infiltrated. The tumor grows slowly.

With desmoplastic variety, elements are rarely multiple. The disease is more common in women and clinically manifested in the form of whitish elements with a westernization in the center and a dense edge.

With multiple trichoepithelioma, individual tumor elements merge into conglomerates. When localized on the auricles, they cause a mechanical occlusion of the auditory canals and in the future - hearing loss. These conglomerates can ulcerate, forming basiliomas. Trichoepithelioma can simultaneously be combined with a syringoma, a cylinder.

The combination of multiple trichoepitheliomas and a cylinder is referred to as Brooke-Spiegler syndrome.

Histopathology. There is an intraspecific malignancy or cysts with clear boundaries surrounded by a layer of basal cells, stromal fibrosis and focal calcification.

Pathomorphology. Usually in a limited area under unchanged zidermis there are various complexes in the size and configuration, the spectrum of which may include primitive "kidneys" similar to the embryonic stage of the hair follicle, the formation of a very bizarre configuration with the presence of structures resembling a partially formed follicle. The cells inside the complexes are obviously flat-epithelial in character, but on the periphery are arranged palisadically. A formation of many keratinized structures such as "horny pearls" is noted. In the zone of keratinization, granules of melanin are often found. Cases with the presence of less differentiated cellular clusters are described, for example, in the case of a solid type of trichoepithelioma, very similar to basal cell. However, with trichoepithelioma, stromal cell infiltration consists of fibroblasts. While in basalioma with piloidal differentiation, stromal infiltration along the periphery of tumor complexes consists of lymphocytes. In trichoepithelioma, there may also be tubular (adenoid) structures, so this tumor is sometimes called epithelioma adenoides cysticum. In some cases, in addition to cellular complexes, a large number of flat-epithelial cysts is noted. Sometimes the contents of the cysts are calcified.

Histogenesis. Foci of solitary trichoepithelioma consist of relatively immature cells, which brings it closer to basal cell. However, the tendency to form hair follicles distinguishes it from the latter. Electron microscopy revealed that horny cysts of trichoepithelioma are immature hair structures in which the cells of the hair matrix directly pass into horn cells. Histochemical study using the Homori method on alkaline phosphatase showed a positive reaction in many intussusceptions on the periphery of tumor islets and strands, which indicates the differentiation of the hair complexes.

It is difficult to distinguish this tumor from basalioma with piloid differentiation, but this is helped by the reaction to alkaline phosphatase, indicating the presence of rudimentary hair complexes in trichoepithelioma.

Differential diagnosis. The disease should be distinguished from Pringle-Burnevel disease, syringoma and basal cell carcinoma.

Treatment of trichoepithelioma. A good effect is the application of cytostatic ointments (30% prospedic, 5% fluorouracil, etc.). Use cryodestruction, electrocoagulation, surgical method, carbon dioxide laser to remove large nodes.