Pilomatrix carcinoma.

The clinicopathologic features of two cases of pilomatrix carcinoma are described and compared with those of the 11 previously reported cases. In contrast with its benign counterpart, pilomatrix carcinoma occurs in older patients and there is a male-predominating sex ratio. The rate of local recurrence is 60%. A single instance of distant metastasis occurred when the tumor recurred locally for the second time. Pilomatrix carcinoma can be accurately diagnosed histologically. The consistent features present in pilomatrix carcinoma but absent in the benign counterpart are increased mitotic activity and cytologic abnormalities including cellular and nuclear enlargement, and vesicular appearance of the nuclei. The primary lesion should be treated aggressively to prevent local recurrence, which may be a factor favoring distant tumor metastasis.