AFP and yolk sac tumor: AFP production in some EOCs is attributed to the foci of yolk sac tumors, such as endometrioid adenocarcinoma with a yolk sac component, mucinous adenocarcinoma with a yolk sac component, clear cell adenocarcinoma with a serous adenocarcinoma component, and endometrioid adenocarcinoma with a clear cell component [1, 8, 17, 19, 27].