Usually benign, non-seminomatous GERM CELL TUMORS that originate from the ovary and are characterized by the presence of tissues which correspond to the different GERM LAYERS. Mature teratomas are composed of well differentiated, adult-type tissues. Immature teratomas are composed of immature, fetal type-tissues. They arise through failure of extrusion of the second POLAR BODY or refusion of it with the ovum. OMIM: 166950
