Ultrastructural study of intracranial yolk sac tumor: with special reference to the oncologic phylogeny of germ cell tumors.

Ultrastructural studies of yolk sac tumors (YST) have generally demonstrated the resemblance of this neoplasm to the primitive human yolk sac. However, these studies have failed to explain the common occurrence of mixed germ cell tumors with yolk sac elements. This report describes the ultrastructural features of a suprasellar YST. This tumor resembled those previously described. Also demonstrated, however, was the presence of primitive germ cells admixed within the neoplasm. A new schema is proposed based on these observations for the interrelationship of germ cell tumors, which may explain the common occurrence of mixed germ cell tumors.