What is Pilomatrix Carcinoma?

Pilomatrix Carcinoma:

Pilomatrixoma, also known as pilomatricoma, and calcifying epithelioma of Malherbe, is an uncommon benign tumor of hair matrix origin. Malherbe and Cheantais first described the lesion in 1880 and originally believed the lesion was a benign tumor of the sebaceous glands. The lesions typically occur on the head and neck and are more common in females. There are two peaks of occurrence with age. The first is before the third decade, with greater than 60% occurring at this time. The second is during the sixth and seventh decades (3). Histologically, pilomatrixomas are characterized by irregularly shaped islands of small basaloid epithelial cells. The basaloid cells generally have small uniform nuclei and scant cytoplasm with indistinct cell borders surrounded by fibrillary material. Also often noted are a variable degree of squamous differentiation and sheets of ghost cells that occasionally are mixed with stroma containing multinucleated giant cells.

Calcifications may or may not be conspicuous. Pilomatrix carcinoma is an exceedingly rare locally aggressive and destructive tumor that usually arises from a pilomatrixoma. Bony invasion and occasional distant metastases have been reported (2). The carcinoma is more common in males than females, with a ratio of 2:1 in a review of 72 cases in the literature (2). Imaging studies such as MRI or CT may be useful to evaluate pilomatrix carcinoma that does not respond to wide local excision with negative margins. Histologically, Pilomatrix carcinoma is characterized by more numerous and atypical mitoses, nuclear atypia, tumor necrosis, and infiltration into subcutaneous fat, blood vessels, nerve and muscle. Aggressive wide local excision is required for treatment.