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TC, neoplasms, tumors, histopathology, Adnexal and Skin Appendage Neoplasms
Dermatology | Neoplasms | Skin and Connective Tissue Diseases
Trichilemmal carcinoma (TC) is a rare, malignant, adnexal neoplasm that is derived from the outer root sheath (ORS) of the hair follicle. These tumors predominantly occur in elderly patients on sun-exposed areas, specifically on the head and neck with the face defined as the most common location. The mean age of diagnosis is 70 years old with a slight male predominance. These lesions are commonly identified as a papular, nodular, and sometimes, exophytic. They generally arise de-novo, but may also derivate from an underlying proliferating trichilemmal cyst with a loss of p53, a seborrheic keratosis, a nevus sebaceous, or a scar. They can be locally aggressive and may exhibit telangiectasias and ulceration due to local destruction.
While the clinical differential diagnosis commonly includes basal cell carcinoma (BCC), squamous cell carcinoma (SCC), and keratoacanthoma, the histopathological differential also includes trichilemmoma, trichoepithelioma, clear cell SCC, clear cell porocarcinoma, and clear cell hidradenocarcinoma. The main differentiating histological feature in a TC is the evidence of trichilemmal keratinization, where the tumor exhibits an absence of granular layer between the stratum spinosum and stratum corneum. The standard of treatment for TC is wide local excision (WLE) with tumor free margins, however, there has been increasing evidence for the efficacy of Mohs micrographic surgery (MMS) in recent years.
Fronek, Lisa F. DO; Brahs, Allyson; Farsi, Maheera DO; and Miller, Richard DO, "A Rare Case of Trichilemmal Carcinoma: Histology and Management" (2020). West Florida Division Virtual Research Day. 28.