Microcystic adnexal carcinoma: a diagnostic and therapeutic challenge.

Microcystic adnexal carcinoma (MAC) is a rare cutaneous neoplasm that is often diagnosed after having been present for a significant period of time. It appears bland on histologic evaluation despite its locally aggressive behavior. Actual skin involvement is significantly more extensive than can be determined clinically and because of this, therapy is challenging. Though metastasis is rare, there have been reports of both regional and distant metastatic disease. Several treatment modalities have been used to date, including standard excision (SE), Mohs micrographic surgery (MMS), irradiation, chemotherapy, and observation. There has also been discussion in the literature regarding techniques than can aid in assurance of clear margins with MMS. We review the literature on MAC, including the various therapeutic options, addressing when one modality may be preferable over others. In general, MMS offers the highest likelihood of clear margins and cure with the fewest procedures.