Endodermal sinus tumor is a malignant tumor of the ovary, also called germ cell tumor. This tumor has a specific tumor marker, elevated alpha-fetoprotein, and occurs mostly in women of adolescent and childbearing age. This tumor can be treated with chemotherapy after surgery because it is very sensitive to chemotherapy and the results are very good. If in early stage, the cure rate through chemotherapy after surgery is very high, and some people are able to complete their reproductive function. If this tumor reaches advanced stage, the cure rate through surgery and chemotherapy after surgery is relatively low, because most of the ovarian tumors are found to be advanced, so it is very important to have a good health checkup once a year.