Endodermal sinus tumor of the mediastinum. Ultrastructural study.

This is the eighth case report of an endodermal sinus tumor of the mediastinum (first case studied by electron microscopy). The ultrastructure of the tumor was found to mimic that of the normal yolk sac and was also similar to that of three previously reported cases of endodermal sinus tumor of the ovary, thus confirming the correctness of Teilum's original interpretation of the tumor as arising in germ cells and differentiating towards extraembryonic structures.