The second subtype is a yolk sac tumor, also called an endodermal sinus tumor, and it's made of germ cells that differentiate into yolk sac tissue.

第二种亚型是卵黄囊瘤，也称为内胚层窦瘤，是由分化为卵黄囊的生殖细胞组成。

The four major types of germ cell tumors are: fetal teratomas, both mature cystic and immature teratomas; yolk sac tumors, or endodermal sinus tumor, choriocarcinoma or placental tissue tumors and finally dysgerminomas or oocyte tumors.

4种卵巢细胞癌如下：畸胎瘤，包括成熟囊性畸胎瘤和未成熟畸胎瘤；卵黄囊瘤，又叫内胚窦瘤；绒毛膜癌，又叫胎盘组织肿瘤；最后是无性细胞瘤，又叫卵母细胞瘤。