Tricholemmoma and Tricholemmal Carcinoma and Cowden Syndrome

Tricholemmoma and tricholemmal carcinoma are tumors of the hair follicle, with the former being benign and the latter malignant. First described in 1962, these tumors typically appear on the head and neck of elderly individuals. Tricholemmoma can present as solitary or multiple papules and is often linked to Cowden syndrome, a genetic disorder marked by various hamartomas and neoplastic growths. Tricholemmal carcinoma manifests as exophytic or polypoid nodules. Dermoscopically, tricholemmoma is characterized by keratin masses with perivascular whitish halos, while tricholemmal carcinoma displays a polymorphous vascular pattern, white-yellowish areas, and ulceration. Differential diagnoses include basal cell carcinoma, squamous cell carcinoma, keratoacanthoma, and viral warts.