Hyaline globules in yolk sac tumor. Histochemical, immunohistochemical and electron microscopic studies

Four cases of yolk sac tumor of the testis and ovary were examined by histochemistry, immunohistochemistry, and electron microscopy, and particular attention was directed toward the close relationship between hyaline globules and alpha fetoprotein (AFP). The hyaline globules were easily identified as eosinophilic globular structures located in the cytoplasm of the tumor cell as well as in the extracellular space. They were considered to be of glycoprotein in nature by their histochemical staining property. By an indirect immunoperoxidase method, the majority of intracytoplasmic hyaline globules were positive for AFP. Electronmicroscopically, the hyaline globules appeared as electron dense bodies with no limiting membranes. They were divided into two types by their electron density and inner structure: one is an electron high dense body consisting of homogeneous or fine granular materials and the other is a moderately electron dense body composed of fine filamentous structures similar to the basement membrane materials. It is suggested that the former corresponds with the AFP positive hyaline globules produces by the tumor cells of visceral type, while the latter represents the AFP negative globules formed by the cells of parietal type in non-neoplastic counterparts.