RESUMEN
Squamous cell carcinoma of the ovary is a very rare malignant tumor originating from malignant transformation of mature cystic teratoma, usually being reported in about 1-3%. It is hard to know the presence of malignant transformation of mature cystic teratoma before operation. So, in case of old age, huge ovarian mass, elevated tumor marker, and operative findings including adhesion, hemorrhage, necrosis and irregular cystic wall, we should suspect malignant transformation. And then we had better do frozen biopsy. Several authors reported the poor prognosis of this malignancy but there is no consensus on optimal therapy because of its rarity. In early stage, curative treatment is possible through only surgical intervention. We experienced a case of squamous cell carcinoma of right ovary developed in a patient with bilateral mature cystic teratomas. We present it with a brief review of literatures.