<prompt> Not a germ cell tumor of ovary:Endodermal sinus tumorPolyembryomaDysgerminomaBrenner tumor  <response>: Germ cell tumors GCT account for 15-20 of ovarian tumors and the vast majority 95 are benign cystic teratomas. The remaining 5 are found principally in children and young adults and have a higher incidence of malignant behavior various germ cell tumors are as under:Mature benign teratomasImmature malignant teratomasMonodermal or highly specialized teratomas DysgenninomasEndodermal yolk sac tumorsChoriocarcinomaEmbryonal carcinoma PolyembryomaMixed germ cell tumors MGCTBrenner tumors are uncommon tumors which account for less than 2 of ovarian neoplasms. These solid neoplasms are characterized by a dense fibrous stroma punctuated by nests of transitional cells resembling those lining the urinary bladder. Brenner tumors are occasionally found in mucinous cyst adenomas suggesting that these tumors arise from coelomic epithelial inclusion cysts through metaplasia of the cyst lining of transitional epithelium. 