Clinical history: 28 year old male, round, skin colored, firm papule on nasolabial fold, slow growing, approximately 4mm in diameter..
What is the diagnosis?
Trichoepitheliomas are typically found as skin colored papules most commonly on the nose, upper lip and cheeks, and can range in size up to 0.5cm in diameter. It is usually seen in young to aging adults, with the hereditary form seen often in younger individuals. There is an equal prevalence between men and women. In the hereditary form, although autosomal dominant, it is more often seen in women, as there is lessened penetrance or expressivity in men.
Histologically trichoepitheliomas are dermal tumors, composed of islands of basaloid cells, which can sometimes show peripheral palisading. Branching nests of basaloid cells are also present. Epithelial structures resembling hair papillae or abortive hair follicles may be seen. Small keratinous cysts lined by squamous epithelium are commonly seen. These cysts can rupture, and cause a small foreign body granulomatous response in the stroma. Focal continuity with the epidermis is seen in up to 33% of cases.
A slow growth is quite characteristic of trichoepitheliomas. Partial removal may result in the persistence or recurrence of this lesion. Although rare, trichoepitheliomas have the potential to develop high-grade carcinomas and mixed epithelial/sarcomatous tumors.
Weedon, D. (2010). Weedon’s skin pathology. Churchill Livingstone Elsevier