Microcystic adnexal carcinoma: forty-eight cases, their treatment, and their outcome.

BACKGROUND Microcystic adnexal carcinoma, or sclerosing sweat duct carcinoma, is an uncommon cutaneous neoplasm associated with extensive local invasion. The standard of care with regard to the best excisional method in treating microcystic adnexal carcinoma has not been established. OBJECTIVES To perform a retrospective study comparing patients treated by Mohs micrographic surgery with those treated by wide excision and to elucidate the epidemiological features of microcystic adnexal carcinoma. PATIENTS AND METHODS A retrospective analysis of a case series involving 48 primary and referral patients diagnosed as having microcystic adnexal carcinoma using standardized criteria. All cases were reviewed by the same dermatopathologists. RESULTS Microcystic adnexal carcinoma predominantly affects the left side of the face of middle-aged women. Microcystic adnexal carcinoma is misdiagnosed 30% of the time. The recurrence rate is 1.98% per patient-year. Mohs micrographic surgery and simple excision show comparable complication rates. Clear margins were obtained in fewer procedures and, therefore, fewer office visits when the lesions were treated with micrographic surgery. The defect surface area after full extirpation following Mohs micrographic surgery was a mean of 4 times that of the clinically apparent size. The wide range of difference between the pre- and the post-Mohs micrographic surgery surface area noted in our data indicates that a margin cannot be safely predicted. CONCLUSIONS Microcystic adnexal carcinoma is a predominantly left-sided, locally aggressive facial tumor, which results in significant morbidity. Our data do not support the use of standardized predictable margins. Mohs micrographic surgery is a reasonable initial treatment, as it accomplishes cure in fewer office visits and does not rely on predicted margins.