A Rare Case of Trichilemmal Carcinoma: Histology and Management.

Trichilemmal carcinoma (TC) is a rare cutaneous tumor thought to be derived from the follicular outer root sheath (ORS). It often manifests as a nondescript skin-colored or pink papule on the hair-bearing, sun-exposed anatomic sites of elderly patients. Trichilemmal carcinoma shows many histologic features reminiscent of follicular ORS-notably, its glycogen-rich clear cells, trichilemmal keratinization, and similar immunostaining profile. Historically, it has been described as following a relatively indolent clinical course, but cases of recurrence, local aggression, and distant metastases have recently been elucidated. Here, we report the case of a 66-year-old male patient who presented with an asymptomatic, erythematous plaque on his neck; biopsy confirmed a diagnosis of TC. The patient deferred Mohs micrographic surgery in favor of wide local excision and was treated successfully with 3-mm margins. Salient histopathologic features, treatment modalities, and management recommendations are discussed.