<prompt> Most frequent epithelial tumors of ovary:Papillary serous cystadenomaBrennersEndometrioidMucinous cyst adenoma  <response>: Ans. a Papillary serous cystadenomaRef. Williams Gynecology, Ch 35; Epithelial tumors of ovaryEpithelial Ovarian Tumor Cell Types Katz: Comprehensive Gynecology, 5th ed. Approximate Frequency Ovarian CancersSerous35-40Mucinous6-10Endometrioid15-25Clear cell mesonephroid5-10BrennerRareSEROUS TUMORS Serous tumors are the most frequent ovarian epithelial tumors. The malignant forms account for 40 or more of ovarian cancers. During frozen section evaluation, psammoma bodies are essentially pathognomonic of an ovarian-type serous carcinomaMUCINOUS ADENOCARCINOMAS About 5 to 10 percent of true epithelial ovarian cancers are mucinous adenocarcinomas These cells resemble cells of the endocervix or may mimic intestinal cells, which can pose a problem in the differential diagnosis of tumors that appear to originate from the ovary or intestine.ENDOMETRIOID ADENOCARCINOMAS About 15 to 25 percent of epithelial ovarian cancers are endometrioid adenocarcinomas, the second most common histologic type.CLEAR CELL TUMORS Comprising 5 to 10 percent of epithelial ovarian cancers, clear cell adenocarcinomas are the most frequently associated with pelvic endometriosis. Microscopically hobnail cells are characteristic finding. These are cells with abundant glycogen and nuclei of the cells protrude into the glandular lumen.BRENNER TUMOR These tumors constitute only 2 to 3 of all ovarian tumors. Brenner tumors consist of cells that resemble the transitional epithelium of the bladder and Walthard nests of the ovary. 