Misdiagnosed microcystic adnexal carcinoma on the lateral forehead and challenges in reconstruction of a large and bone-deep defect.

Background: Microcystic adnexal carcinoma (MAC) is a rare cutaneous malignancy characterized by aggressive local infiltration, including a high propensity for perineural invasion. Histologically it can be easily confused with benign adnexal tumors, which often leads to inappropriate initial treatment. As a consequence delayed surgical excision often requires removal of large cutaneous masses which can be followed by challenges in reconstruction.