Immunohistochemical study of hepatic and enteric structures in testicular endodermal sinus tumors.

Features of hepatic and enteric tissue have been detected in serial sections of 2 out of 6 endodermal sinus tumors (EST) and embryonal carcinomas of the testis showing endodermal sinus areas. Hepatic nests, which appeared as tubules, cords and giant multinucleated cells, were PAS-positive as well as immunoreactive for alphafetoprotein (AFP) and cytokeratin (CK). Enteric tubules were found within EST areas and were characterized by their lack of cell atypism. The presence of diffuse PAS-, AFP- and CK-reactivity in cytoplasm, together with a brush border or an apical staining for CEA, were quite distinctive. EST showed a potential for both intra- and extraembryonal endodermic development and may be interpreted as a monophyletic teratoma.