This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Unknown
[{'content': 'Not a germ cell tumor of ovary: \nSelect and explain. \nA. Endodermal sinus tumor, B. Polyembryoma, C. Dysgerminoma, D. Brenner tumor', 'role': 'user'}, {'content': 'Answer: D \nExplanation: 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:\n\nMature (benign) teratomas\nImmature (malignant) teratomas\nMonodermal or highly specialized teratomas\xa0\xa0\xa0\xa0\xa0\xa0\xa0\xa0\xa0\nDysgenninomas\nEndodermal (yolk) sac tumors\nChoriocarcinoma\nEmbryonal carcinoma\xa0\xa0\nPolyembryoma\nMixed germ cell tumors (MGCT)\n\nBrenner 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.', 'role': 'assistant'}]