Microcystic Adnexal Carcinoma Misdiagnosed as Desmoplastic Trichoepithelioma on Preoperative Biopsy.

Microcystic adnexal carcinoma is a rare type of tumor, with about 300 cases reported globally. Due to its similar histology with other tumors, it is occasionally misdiagnosed as desmoplastic trichoepithelioma, basal cell carcinoma, syringoma, and so on. We present a patient with a mass on the perioral area who was preoperatively diagnosed with trichoepithelioma. Microcystic adnexal carcinoma was diagnosed after excisional biopsy and a wide excision. Defects were reconstructed with a mucosal advancement flap. There was no recurrence and there were no significant complications during the 18-month follow-up period. Because superficial punch biopsy has limitations in width and depth, surgeons should always consider the possibility of malignancy of a mass even if a biopsy shows a benign result.