Adenocarcinoma arising in mature cystic teratoma: a case report.

Benign cystic teratoma is recognized as one of the most common tumors in women during the reproductive age and frequently is treated by pelviscopic operation. Malignant transformation of a benign cystic teratoma is a rare event, and adenocarcinoma is extremely rare, and distinguishing this malignant change from benign disease preoperatively is nearly impossible even by the use of radiological imaging or various tumor markers. Therefore, patients should be informed that if a laparoscopic cystectomy is undertaken, a prompt second staging operation should be performed if the definitive pathology reveals an unexpected malignancy. We present a case with thyroid papillary carcinoma of follicular variant arising from mature cystic teratoma removed by laparoscopic salpingo-oophorectomy followed by staging laparotomy. We briefly reviewed literatures with regard to malignant transformation of a benign cystic teratoma.