Pilomatrix carcinoma is a rare malignant variant of pilomatricoma, which is a firm, slow-growing, dermal or subcutaneous tumor that was first described in 1880. At that time, pilomatricomas were believed to be benign tumors of sebaceous gland origin. However, in 1942, they were correctly determined to be of hair cortex cell origin.1 They have a bimodal age distribution, with the majority presenting in the first 3 decades of life and a smaller peak in the sixth and seventh decades. They also have a predilection for the head and neck, with a lower occurrence rate on the extremities and trunk,1 and they are composed of 3 types of cells: basophilic, ghost, and transitional. In longer-standing tumors, the amount of basophilic and transitional cells decrease as the ghost cell population increases.2 Subtypes include perforating, atypical, invasive, proliferating, and aggressive pilomatricomas.3 In 1980, Lopansri and Mihm4 reported the first case of a malignant pilomatrixoma. At that time, they coined the terms pilomatrix carcinoma and calcifying epitheliocarcinoma of Mahlerbe. In 2001, Hardisson et al5 found only 63 cases reported in the literature.
Pathology Quiz Case 2—Diagnosis. Arch Otolaryngol Head Neck Surg. 2007;133(8):842. doi:10.1001/archotol.133.8.842