Trichoepithelioma

The Trichoepithelioma ( Adenoid cystic epithelioma Brooke, Haarbalgfehlknötchen ) is a benign intradermal localized skin tumor derived from cells of the hair follicle or differentiated in their direction. In addition to a sporadic form with individually occurring tumors ( solitary trichoepithelioma ) one knows a familial, autosomal dominant hereditary form, are observed in multiple tumors (multiple trichoepitheliomas ).

Epidemiology

Solitary trichoepitheliomas usually occur in adolescents and younger adults. The hereditary multiple trichoepitheliomas manifest themselves, however, often already in childhood or adolescence and can be observed due to a reduced expressivity and penetrance in men preferred women. About the incidence of Trichoepithelioms are no accurate data. A dermatopathologisches laboratory with a Specimen of around 9000 cases reported annually of about 2-3 diagnoses per year.

Etiology

The familial form of Trichoepithelioms mutations underlie a tumor suppressor gene on chromosome 9p21. In other cases, there is an association with Brooke- Spiegler syndrome with mutations on chromosome 16q12 - 13th These patients show in addition to an increased incidence of Trichoepitheliomen more tumors of the skin appendages such as dermal cylindromas or Spiradenome.

Pathology

Macroscopically trichoepitheliomas appear as rounded, skin-colored, 2-8 mm in diameter papules that occur mainly in the area of the nasolabial fold, nose, upper lip, forehead and scalp. 50 percent of the lesions can be found here on the face and scalp. Occasionally, a manifestation in the neck or upper torso is observed. In the familial form, there are often multiple tumors, especially in the area of ​​the nasolabial fold. In the so-called giant solitary Trichoepitheliomen there are usually variations of the Trichoblastoms. Histologically trichoepitheliomas appear as well-circumscribed and confined to the upper dermis, symmetrical basaloid epithelial cell complexes, which are embedded in a fibrous stroma or fibromyxoides. Occasionally, let hair papillae, abortive hair follicles or keratin - containing cysts detected. Apoptosis and mitotic figures are rarely observed, necrosis, however, do not occur. A histological variant is the desmoplastic trichoepithelioma, which is characterized by compact connective tissue in the surrounding area of the epithelial tumor cell groups.

Immunohistochemistry

The tumor cells express cytokeratins the outer hair root sheath ( cytokeratins 5, 6, 8 and 17). The marker bcl- 2 is mainly in the peripheral layer of cells of tumor cell nests a positive signal. Immunohistochemical differences from basal cell carcinoma, the lack of expression of androgen receptors in cancer cells and the CD10 positivity of stromal cells.

Diagnosis

The diagnosis is made on surgically removed tumor or a biopsy by the pathologist. Differential diagnosis includes basal cell carcinoma clinically the small nodular or dermal nevi. Multiple trichoepitheliomas must be distinguished from angiofibromas in tuberous sclerosis and multiple basal cell carcinomas in the Gorlin - Goltz syndrome. Histological differential diagnoses include basal cell carcinoma, the Trichoadenoma, the Trichofolliculoma, microcystic adnexal carcinoma or the follicular hamartoma a basaloides.

Therapy

Method of choice is surgical removal of the tumor. When multiple tumors this can be problematic and do a skin graft or laser surgery required. It is also possible dermabrasion, in which the lesion is removed only superficial. Here, the tumor is, however, often within months to years again.

Forecast

Trichoepitheliomas show a slow growth. With only partial removal of recurrences occur. In rare cases, a degeneration and a transition to a carcinoma or a malignant epithelial- mesenchymal mixed tumor has been described.