Mature cystic teratoma coexisting with clear-cell carcinoma in the ovary

Mature cystic teratoma (MCT) is the most common benign ovarian tumor; clear-cell carcinoma (CCC) is a relatively common malignant ovarian tumor in Japan, but there are few reports on the coexistence of MCT and CCC. Here we report a case of simultaneous MCT and CCC in the ovary and review the relevant literature. The patient was a 49-year-old woman. A 5-cm MCT was found in the left ovary on initial gynecological examination, and she was referred to hospital for treatment because it was expanding. Magnetic resonance imaging showed a multilocular cystic tumor 16 × 10 × 9.5 cm in the left ovary, and surgery was performed. The final pathological diagnosis was MCT, endometriotic cyst, clear-cell adenofibroma, clear-cell borderline tumor, and CCC in the left ovary.