Carcinoma arising in sebaceous and epidermoid cysts.

Malignant degeneration of sebaceous and other epidermoid cysts in uncommon, but it does occur in approximately 2.2% of cysts examined. It should be suspected in patients with atypical appearance or a history of cyst recurrence. All cysts should be examined histologically and the histological grade carefully noted. This paper reports a well-differentiated squamous cell carcinoma arising in an epidermoid cyst. Wide excision was performed, including superficial parotidectomy, because of histological evidence of extension beyond the cyst. Based on the literature, recurrence or metastasis of our patient's tumor appears unlikely.