Trichoepithelioma

Classification according to ICD-10
8100/0	Trichoepithelioma
ICD-10 online (WHO version 2019)

Solitary trichoepithelioma of the facial skin in a young woman.

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

Epidemiology

Solitary trichoepitheliomas mostly occur in adolescents and younger adults. Hereditary multiple trichoepitheliomas , on the other hand, often manifest themselves in childhood or puberty and are primarily observed in women due to a reduced expressivity and penetrance in males . Exact data are not available on the incidence of trichoepithelioma. A dermatopathological laboratory with an examination of around 9,000 cases annually reported about 2–3 diagnoses per year.

etiology

The familial form of trichoepithelioma is based on mutations in a tumor suppressor gene on chromosome 9p21. In other cases there is an association with Brooke-Spiegler syndrome with mutations on chromosome 16q12-13. In addition to an increased incidence of trichoepithelioma, these patients also have other tumors of the skin appendages such as dermal cylindromas or spiradenomas .

pathology

Histology of trichoepithelioma: basaloid tumor cell nests in the upper dermis.

Histology of trichoepithelioma: tumor cell formations at higher magnification.

Macroscopically , trichoepitheliomas appear as rounded, skin-colored papules 2–8 millimeters in diameter , which mainly occur in the nasolabial fold , nose, upper lip, forehead and scalp. 50 percent of the lesions are found on the face and scalp. Occasionally, a manifestation in the neck or upper trunk area is also observed. In the familial form, multiple tumors are often found, especially in the area of the nasolabial fold. The so-called giant solitary trichoepitheliomas are mostly variants of trichoblastoma .
Histologically , trichoepitheliomas appear as well-circumscribed , symmetrical basaloid epithelial cell complexes confined to the upper dermis and embedded in a fibrous or fibromyxoid stroma. Occasionally, hair papillae, abortive hair follicles or keratin- containing cysts can be detected. Apoptosis and mitosis figures are rarely observed, but necrosis does not occur. A histological variant is desmoplastic trichoepithelioma , which is characterized by compact strands of connective tissue in the vicinity of the epithelial tumor cell groups.

Immunohistochemistry

The tumor cells express cytokeratins of the outer hair root sheath (cytokeratins 5, 6, 8 and 17). The marker bcl-2 shows a positive signal mainly in the peripheral cell layer of the tumor cell nests. Immunohistochemical differences from basal cell carcinoma are the lack of expression of androgen receptors in tumor cells and the CD 10 positivity of stromal cells.

diagnosis

The diagnosis is made on the surgically removed tumor or on a biopsy by the pathologist . Clinically, small-nodular basal cell carcinoma or dermal nevi have to be differentiated from the differential diagnosis . Multiple trichoepitheliomas must be differentiated from angiofibromas in tuberous sclerosis and multiple basal cell carcinomas in Gorlin-Goltz syndrome or Rombo syndrome .

Histological differential diagnoses are basal cell carcinoma , trichoadenoma , trichofolliculoma , microcystic adnexal carcinoma, or basaloid follicular hamartoma .

therapy

The method of choice is surgical removal of the tumor. In the case of multiple tumors, this can be problematic and require a skin graft or laser surgery. It is also possible dermabrasion , where the lesion is removed only superficially. Here, however, the tumor often recurs within months to years.

forecast

Trichoepitheliomas show slow growth. If it is only partially removed, recurrences occur. In rare cases, degeneration and transition to carcinoma or a malignant mixed epithelial - mesenchymal tumor have been described.

Individual evidence

↑ ^a ^b ^c ^d H. Kerl, C. Garbe, L. Cerroni, HH Wolff: Histopathologie der Haut . Springer, 2003, ISBN 3-540-41901-2 .
^ Pschyrembel Clinical Dictionary . Founded by Willibald Pschyrembel. Edited by the publisher's dictionary editor under the direction of Helmut Hildebrandt. 261st edition. De Gruyter, Berlin 2007, ISBN 978-3-11-018534-8 .
↑ ^a ^b ^c ^d ^e ^f ^g ^h ⁱ ^j V. G. Prieto, CR Shea: Trichoepithelioma (November 19, 2008); http://emedicine.medscape.com/article/1060049-overview

[kerl-1] H. Kerl, C. Garbe, L. Cerroni, HH Wolff: Histopathologie der Haut . Springer, 2003, ISBN 3-540-41901-2 .

[pschyrembel-2] Pschyrembel Clinical Dictionary . Founded by Willibald Pschyrembel. Edited by the publisher's dictionary editor under the direction of Helmut Hildebrandt. 261st edition. De Gruyter, Berlin 2007, ISBN 978-3-11-018534-8 .

[emedicine-3] ↑ ^a ^b ^c ^d ^e ^f ^g ^h ⁱ ^j V. G. Prieto, CR Shea: Trichoepithelioma (November 19, 2008); http://emedicine.medscape.com/article/1060049-overview