Multiple Trichoepithelioma D23.-

Biphasic (epithelial-mesenchymal) adnexal tumour with differentiation towards follicular germ cells and the specific follicular stroma. Conventional tricheopthelioma (also: cribriform trichoblastoma) is included in the trichoblastoma group. It may be solitary and/or multiple. See also adnexal tumours with hair follicle differentiation. It is the predominant tumour type in Brooke-Spiegler syndrome. At present, the question as to what extent Brooke-Spiegler syndrome and the syndrome of multiple familial trichoepitheliomas belong to an identical group of diseases has not been completely clarified. Some authors also refer to the syndrome of multiple trichoepitheliomas as Brooke syndrome and distinguish Brooke-Spiegler syndrome as a syndrome with multiple trichoepitheliomas, cylindromas and spiradenomas.

Autosomal dominant inheritance in multiple familial trichoepitheliomas, see Brooke-Spiegler syndrome.

• In type I a heterogeneous mutation is found in the CYLD gene (16q12.1 - allelic: familial cylindromatosis, Brooke-Spiegler syndrome).
• In type II there is a mutation in a gene localized at 9p21.

Often occurring in adolescence.

Mostly multiple, symmetrically arranged, completely painless and irritation-free, rough, hemispherical, 0.2-0.5 cm in size, usually glassy, skin-coloured, rarely red, firm nodules, the surface of which is sometimes covered with telangiectasias.

In case of multiple occurrence (which is the normal case), combinations with hemangiomas, dental cysts, cylindromas, spiradenomas (see also Brooke-Spiegler syndrome) and ovarian fibromas are possible.

Proliferation of basal cells, epithelial or prickly cells with basaloid strands, which occasionally show pilous formations, restricted to the dermis. The abundant connective tissue stroma resembles follicular papillae and the perifollicular binovular sheath. Focally, the stroma may dominate the histological picture. Immunohistology: Trichoepitheliomas in contrast to basal cell carcinoma show a diffuse staining by the antibody PHLDA1. Basal cell carcinoma: PHLDA1-negative.

Basal cell carcinoma: No symmetry in appearance, no preferential disseminated nasolabial involvement pattern. Histology: Basal cell carcinoma PHLDA1 negative.

Cylindromas: Either solitary or multiple occurrences. V.a. capillitium; nodules or nodes are significantly larger. Brooke-Spiegler syndrome should be distinguished from solitary cylindromas (multiple cylindromas possibly in combination with other adnexal tumors).

Syringoma: Mostly occurring in plural, barely 0.2 cm large skin-colored nodules, mostly localized in the eyelid region.

Adenoma sebaceum: Multiple reddish-brownish, rarely skin-colored, soft, 0.2-0 cm, asymptomatic papules. Acneiform picture.

Excision of cosmetically disturbing tumours.

In the case of disseminated tumours, therapy with the CO ₂ laser or the erbium YAG laser.

Alternatively: cryosurgery or dermabrasion.

Recurrences are frequent (almost obligatory), usually occurring after about 2 years.

Favourable; development of basal cell carcinoma possible. Transformation into trichoblastic carcinoma is an absolute rarity (2 cases in the world literature, see case report).

According to the currently valid WHO classification, the "classical trichoepithelioma" is called cribriform trichblastoma or conventional trichoepithelioma.

A 63-year-old man presented with an ulcerated nodular lesion over the glabella and multiple asymptomatic nodular lesions over the face, scalp, chest, and limbs. His father, grandfather and paternal cousins suffered from similar nlesions. Histopathological examination revealed trichoblastic carcinoma arising from trichoepithelioma over glabella. Thus, the diagnosis of Brooke's syndrome with malignant transformation of trichoepithelioma was made. A trichoblastic carcinoma arising from a trichoepithelioma in a patient with Brooke's disease is extremely rare, with only one case described in the literature (Jayalakshmy P et al 2018).

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