Concurrent pilomatrix carcinoma and giant pilomatrixoma

A 52-year-old man presented with a large, fungating mass on the inner aspect of his left thigh and a smaller hard mass on the inner aspect of his left knee with normal overlying skin. Both lesions had first been noted by the patient 1 year previously and for the first 6 months had a similar appearance until the thigh mass rapidly increased in size and fungated. Pathology of the large thigh lesion showed pilomatrix carcinoma while that of the smaller knee lesion was typical of pilomatrixoma. The pilomatrix carcinoma was widely excised and there has been no evidence of recurrence or metastasis after 3 years. The clinical course of the thigh lesion suggested that pilomatrix carcinoma may arise from a pre-existing pilomatrixoma. On review of the literature, pilomatrix carcinoma of the lower limb may be more likely to metastasize than those on other sites.