Malignant proliferating trichilemmal tumors arising in patients with multiple trichilemmal cysts: A case series

Abstract

Proliferating trichilemmal tumors (PTTs) are rare tumors that arise from the outer root sheath of the hair follicle. They typically occur on the scalp of elderly women and commonly correspond to transformation of a simple trichilemmal cyst (TC).1-4 PTTs can reach sizes up to 25 cm and are most often benign, but malignant transformation is possible with the presence of local invasion, atypia, and necrosis. Clinically, malignant proliferating trichilemmal tumors (MPTTs) present as rapidly growing exophytic ulcerated tumors.