Ultrastructural observation of alpha-fetoprotein producing cells in human hepatocellular carcinoma using immunoperoxidase methods--comparison with fetal liver.

The precise sites of alpha-fetoprotein (AFP) synthesis and ultrastructural features and differences of AFP-producing cells were observed in periodate-lysine-paraformaldehyde fixed, frozen liver tissues from four human hepatocellular carcinoma (HCC) patients and three human fetuses using the direct (horseradish peroxidase-labeled Fab' fraction of anti-human AFP) immunoperoxidase method. We demonstrated that AFP was located in the membrane and cisternae of rough endoplasmic reticulum, membrane-bound ribosomes, perinuclear space and Golgi apparatus. The location and intensity of immunoreaction products of AFP in hepatoma cells varied from cell to cell and case to case, while these features tended to be regular in fetal hepatocytes. We did not observe ultrastructural differences between AFP-producing and non-producing cells adjacent to each other. These observations indicate that AFP production does not occur in morphologically distinct cell populations of hepatoma tissue and that hepatoma tissue is functionally much more heterogeneous than fetal liver.