<prompt> Which of the following is the most common malignant ovarian tumor?Serous cysadenocarcinomaMucinous tumorEndometrioid tumorMesonephroid tumor  <response>: 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. 