Tissular immunoenzymatic detection of hepatic alphafetoprotein in human hepatomas

5 human cases of hepatoma have been chosen with respect to their different seric alpha-fetoprotein (alpha-FP) level and histological characters. Cells producing alpha-FP have been studied with specific horseradish-peroxidase-labelled immunoglobulins. Ultrastructural examination shows that alpha-FP is present in the cytoplasm of some tumoral hepatocytes. alpha-FP is also present in the cytoplasm of some rare nontumoral hepatocytes of a nonsecreting hepatoma. Ultrastructural differences are described in tumoral hepatocytes according to the grade of differentiation of the tumoral cell population. alpha-FP production appears to be restricted to moderately differentiated tumoral hepatocytes. These observations led to the hypothesis that production of alpha-FP may transiently develop either during the differentiation of tumoral hepatocytes, or during the new differentiation of nontumoral hepatocytes involved in a proliferative process.