A yolk sac tumor that occurs in an adult. The disease is Monarch Disease Ontology identifier MONDO_0003404 (adult yolk sac tumor). Also known as: adult endodermal sinus neoplasm, adult endodermal sinus tumor, adult endodermal sinus tumour, adult yolk Sac neoplasm, adult yolk Sac tumor, adult yolk Sac tumour, yolk sac tumor of adults, yolk sac tumour of adults.