Histologic and immunohistochemical studies of alpha-fetoprotein (AFP)-producing gastric carcinoma.

Five gastric adenocarcinomas and their metastatic nodules in the liver with high serum AFP levels were examined by histologic and immunohistochemical methods. The examination revealed that AFP-producing stomach cancers were poorly differentiated carcinoma cells, especially with medullary arrangements, or pleomorphic or multinucleated giant cells. Well-differentiated papillotubular adenocarcinoma tissues on the glandular epithelium were not stained with anti-AFP. One out of the five AFP-producing adenocarcinomas with medullary patterns resembled liver cell carcinoma on light microscopy. However, an ultrastructural study showed tumor cells of the intestinal type, since the cells possessed a ductal lumina with abundant microvilli and a secretory granules. The findings suggest that the tumor cells differentiated in an intestinal direction rather than hepatic direction. In addition, we noted three simultaneously CEA-positive cases out of five AFP-producing gastric carcinomas. CEA was strongly stained in well differentiated adenocarcinoma tissues in the glandular epithelium or in areas of medullary type carcinoma invasion. However, CEA was not detected in undifferentiated carcinoma cells.