Microcystic Adnexal Carcinoma

Microcystic adnexal carcinoma (MAC) is a rare malignant sweat gland tumor that commonly occurs on the head and neck. MAC has a predilection for the central face but may be found although it may be found on the trunk, axilla, extremities, and genitals. MAC is characterized by its slow growth but local aggressiveness. There are approximately 200 cases worldwide; however, it was Goldstein and others that first described MAC in 1982.  MAC has been mentioned under a number of names, including: Sclerosing sweat duct carcinoma (SSDC). Malignant syringoma. Syringoid eccrine carcinoma. Eccrine epithelioma. Syringomatous carcinoma. Sweat gland carcinoma with syringomatous features. The tumor, known as syringomatous adenoma of the nipple, has been considered MAC; however, this is debated. MAC is known to have perineural invasion (upwards of 80%) with infiltration beyond clinically apparent margins. However, it has little metastatic potential but often recurs.