Trichoepithelioma D23.-

Conventional trichoepithelioma is a rare benign neoplasm of the adnexa. It can occur as a solitary or multiple adnexal tumor. Very rare is the autosomal dominantly inherited familial form (OMIM 601606, OMIM 612099). The latter is also known as Brooke syndrome. Familial trichoepitheliomas are to be distinguished from Brooke-Spiegler syndrome (OMIM 605041), a genodermatosis in which, in addition to trichoepitheliomas, cyldindromes and also spiradenomas are expressed.

Most commonly, trichoepithelioma develops as a slow-growing, inconspicuous, skin-colored or pearly solid nodule 0.5-1.0cm in size. Ulceration is uncommon. The diagnosis is made histologically (Kang KJ et al (2019).

Proliferation of basal cells, epithelial or spiny cells with basaloid strands confined to the dermis, occasionally showing pilary formations. The abundant connective tissue stroma is reminiscent of follicular papillae and perifollicular binge tissue sheaths. Focally, the stromal reaction may dominate the histologic picture. Immunohistology: Trichoepitheliomas clearly express PHLDA1 on. The basal cell carcinoma: PHLDA1 negative (Sellheyer K et al. 2011).

Basal cell carcinoma

The very rare desmoplastic tricheopithelioma is considered a histological variant of the "conventional" trichoepithelioma (Rahman J et al. 2020).

Surgical excision is the standard treatment. Regular follow-up care should be given.

The "giant solitary variant" of trichoepithelioma developing in later life is very rare. 19 cases in the world literature are noted (Teli B et al. 2015).

1. Kang KJ et al (2019) Trichoepithelioma Misdiagnosed as Basal Cell Carcinoma. J Craniofac Surg 30:e197-e199.
2. Rahman J et al. (2020) Desmoplastic trichoepithelioma: Histopathologic and Immunohistochemical Criteria for Differentiation of a Rare Benign Hair Follicle Tumor From Other Cutaneous Adnexal Tumors. Cureus 12:e9703.
3. Sellheyer K et al. (2011) PHLDA1 (TDAG51) is a follicular stem cell marker and differentiates between morphoeic basal cell carcinoma and desmoplastic trichoepithelioma. Br J Dermatol 164:141-147.
4. Sharma S et al (2018) Dermoscopy of trichoepithelioma: A Clue to Diagnosis. Indian Dermatol Online J 9:222-223.
5. Stoica LE et al (2015) Solitary trichoepithelioma: clinical, dermatoscopic and histopathological findings. Rome J Morphol Embryol 56(2 Suppl):827-832.
6. Tebcherani AJ et al. (2012) Diagnostic utility of immunohistochemistry in distinguishing trichoepithelioma and basal cell carcinoma: evaluation using tissue microarray samples. Mod Pathol 25:1345-1353.
7. Teli B et al (2015) Giant solitary trichoepithelioma. South Asian J Cancer 4:41-44.