ABSTRACT
Malignant transformation of mature cystic teratoma (MCT) is an uncommon complication occuring in approximately 1-3%. Any of the constituent tissues of a teratoma has the potential to undergo malignant transformation; squamous cell carcinoma is the most commonly associated cancer, however, adenocarcinomas or carcinoid tumors arising in mature cystic teratoma are uncommon, especially simultaneously. We present an unusual case of postmenopausal women having mucinous adenocarcinoma and strumal carcinoid tumor simultaneously arising in one of bilateral mature cystic teratoma of the ovary. We suggest malignant transformation of MCT should be treated according to the management of the worst histologic diagnosis of the transformations if there are 2 or more malignancies are arised in MCT of the ovary.