Endodermal Sinus Tumor
An unusual and aggressive tumor of germ-cell origin that reproduces the extraembryonic structures of the early embryo. It is the most common malignant germ cell tumor found in children. It is characterized by a labyrinthine glandular pattern of flat epithelial cells and rounded papillary processes with a central capillary (Schiller-Duval body). The tumor is rarely bilateral. Before the use of combination chemotherapy, the tumor was almost invariably fatal. (From DeVita Jr et al., Cancer: Principles & Practice of Oncology, 3d ed, p1189)