A rare case of trichilemmal carcinoma in a sun-unexposed area

Trichilemmal carcinoma is an uncommon skin tumor that originates from the follicular outer root sheath. It frequently appears on the hair-bearing, sun-exposed anatomic locations of older people as an unremarkable, skin-colored, or pink papule. Trichilemmal carcinoma looks a lot like follicular outer root sheath regarding its histology, especially its glycogen-rich clear cells, trichilemmal keratinization, and immunostaining profile. The diagnosis of trichilemmal carcinoma depends on histological analysis, with immunohistochemistry, if necessary, due to its ability to resemble numerous different clinical entities. Commonly, it has a relatively indolent clinical course but can rarely have recurrence, local aggression, or distant metastases. Surgical excision is considered the first choice for curative treatment. Here, we report a rare case of trichilemmal carcinoma in a 66-year-old female patient who presented with an ulcerated and fungated mass over the left proximal anteromedial leg for the past five years, which was histomorphologically confirmed to be trichilemmal carcinoma. This excision of the mass with a clean margin was tried, and she is on active follow-up. Considering the rarity of trichilemmal carcinoma presenting in an unexposed area, we would like to introduce this case to the world. To our knowledge, this is the first case to be reported in our country.