and functionally from ordinary endothelia. 2,3 SECs play an To examine the phenotype of the sinusoidal endothelial important role in the receptor-mediated clearance of various cells (SECs) surrounding tumor cells and the process of capilmacromolecules from the blood, including small particulate larization in hepatocellular carcinoma (HCC), 51 primary substances. In chronic hepatitis and cirrhosis, SECs frequently undergo CD4, CD14, and/or CD32 were found on HCC SECs only in transformation into capillary ECs possessing a basement 12 well-differentiated primary HCCs showing a thin trabecumembrane and no fenestrae, i.e., capillarization, 13 and they lar or pseudoglandular tumor cell arrangement. These 12 tulose some of their phenotypic features (including FcR expresmors were smaller than those without CD4-, CD14-, and/or sion) regardless of whether sinusoidal capillarization oc-CD32-positive SECs (P õ .05). Among them, 7, 5, and 11 curs. 8,14 In hepatocellular carcinoma (HCC), the endothelia tumors were negative or only partially positive for laminin, of the sinusoids, i.e., the blood vessels surrounding tumor PAL-E Ag, and FVIIIRAg, respectively. Staining for laminin cells, is generally considered to resemble the capillary endoand PAL-E Ag showed an inverse relationship to the expresthelia, 15,16 but several studies have indicated that the sinusoision of CD4, CD14, and CD32 on HCC SECs and the tumor dal endothelia of early HCC contains Kupffer cell-like macdifferentiation. In conclusion, the phenotypes of the SECs in rophages, 17,18 and shows morphological characteristics early and well-differentiated HCC are thought to be similar intermediate between those of ordinary capillary endothelia to those of the SECs in normal liver. With progressing tumor and the sinusoidal endothelia in normal liver. 19,20 It seems dedifferentiation the HCC SECs lose the phenotypes peculiar that the phenotypes of the SECs in HCC (HCC SECs) graduto liver SECs and acquire the characteristics of capillary ECs, ally changes into that of capillary ECs with tumor progresthough both types of phenotypical change occur indepension. However, the change in the expression of the receptors dently of each other. (HEPATOLOGY 1997;26:407-415.) and adhesion molecules specifically detected on SECs are unclear. This is important for understanding not only the Hepatic sinusoidal endothelial cells (SECs) are unique biological nature of HCC SECs, which are major stromal cells endothelial cells (ECs), which possess fenestrae and no basesupporting HCC cells, but also the pathobiology of sinusoidal ment membrane, and reside together with tissue-fixed macrocapillarization. phages, i.e., Kupffer cells. 1 SECs differ both morphologicallyIn the present study, to analyze the relationship between the phenotypes of SECs and sinusoidal capillarization in