Microcystic adnexal carcinoma (sclerosing sweat duct carcinoma)

Microcystic adnexal carcinoma (MAC) is a recently described malignant neoplasm of the adnexal structures of skin that shows a marked propensity for early infiltrative and locally aggressive growth. Its banal clinical appearance may lead to a delay in diagnosing the tumor by biopsy, and its multifaceted histologic features may lead to an incorrect tissue diagnosis. Confusion with benign tumors and less aggressive malignancies can lead to inadequate initial treatment and extensive recurrences. We describe three cases of microcystic adnexal carcinoma and review the clinical and histologic features, treatment, and prognosis of this neoplasm.