Microcystic adnexal carcinoma (MAC) is a rare malignant tumor of skin appendages. MAC grows slowly, but is locally aggressive. The metastatic potential is low, but the recurrence rates are very high owing to insufficient dissection. The most common location of MAC is the skin of the midface of middle-aged adults. There has been no report about MAC arising in the gingiva. We report here an extremely rare case of MAC of the upper gingiva in a 53-year-old woman. She presented to our hospital with a 6-year history of a gradually increasing gingival mass. Intraoral examination revealed a smooth, poorly circumscribed mass with white granules resembling Fordyce spots on her upper gingiva. There was no bone destruction or regional lymph node swelling. The histopathological diagnosis was a tumor of skin appendages. Tumor resection was performed. Postoperative pathological examination revealed that the tumor differentiated into hair follicles and the sweat-gland-like structures and deeply infiltrated into muscle, perineural spaces, and bone. Since the surgical margins were positive, additional resection was performed after preoperative mapping biopsy. Finally, the tumor was completely excised. No tumor recurrence or metastasis have been observed over 1 year.
