Which of the following is the most common malignant ovarian tumor?

Ans. is 'a' i.e., Serous cystadenocarcinoma o Serous cysadenomas or cysadenocarcinomas form about 50% of all the ovarian tumors. Of these 60 - 70 % are benign, 15% borderline malignant, and 20 - 25% malignant. Thus serous cystadenocarcinomas form the most common malignant tumors of ovary.