An immuno-electron microscopic study on intra and extracellular localization of alpha-fetoprotein in human...

Intra and extracellular localization of alpha-fetoprotein (AFP) has been studied by an indirect peroxidase labeled antibody method using 12 cases of human hepatocellular carcinoma (HCC). With light microscopic observation, positive immuno-staining for AFP was observed in 6 out of 12 cases and demonstrated as granular or diffuse deposits in the cytoplasm of neoplastic hepatocytes. In electron microscopic studies, 8 cases showed the positive immuno-staining for AFP in the neoplastic hepatocytes. Intracellular antigen was well circumscribed within certain cell organelles with the positive immuno-staining for AFP being observed in perinuclear space, cisternae of rough endoplasmic reticulum (RER), Golgi complexes, and secretory vesicles. In addition, the positive immuno-staining for AFP was observed in bile canaliculus-like space in most cases with increased levels serum AFP and in some cases which showed normal levels of serum AFP. Furthermore, the positive immuno-staining for AFP was also observed in intercellular, Disse's-like and sinusoid-like spaces, and micropinocytotic and lysosome-like vesicles in the endothelial cells in a few cases which showed excessively high value of serum AFP.