Malignant proliferating trichilemmal tumors (MPTTs, malignant proliferating pilar tumors) are theorized to originate from the outer root sheath of the hair follicle which resembles the isthmic portion of the hair follicle and epithelium of the lower hair follicle in catagen phase.1 They may develop de novo or arise from a pre- existing trichilemmal cyst or proliferating trichilemmal tumor. The tumors typically present with rapid growth on the scalps of women over the age of 50. In this review, we present two cases of MPTT, presenting on the scalp of a 69-year-old woman and the scalp of a 53-year-old woman. Both tumors were successfully treated with surgery and radiation. In addition to the classic histologic features, pilomatrical differentiation was also seen in case 1, a histologic feature that has rarely been described. In this paper, we review previously reported cases and summarize basic demographics, lesion size, location, treatment method, and patient outcome.
Keywords: malignant proliferating pilar tumor; malignant proliferating trichilemmal tumor; proliferating pilar tumor; trichilemmal cyst.