Abstract: ObjectiveTo study the significance of the expression of endothelial cell specific molecule 1 (ESM-1) in hepatocellular carcinoma (HCC). MethodsThe molecular profile of endothelium was studied through gene expression profiling technique in 3 cases of HCC and their respective paraneoplastic tissue. The expressions of ESM-1 in 100 samples of HCC and their corresponding paraneoplastic tissues and 16 samples of normal liver tissues were studied through immunohistochemistry assay. ResultsOne hundred and twelve genes was differentially expressed in 3 cases of HCC, including 6 genes which were functionally correlated with endothelial cells. ESM-1 was one of the 6 genes. ESM-1 was specifically expressed in the endothelium of HCC tissues and no expression was found in the paraneoplastic liver tissues and normal liver tissue. The expression of ESM-1 in HCC with microscopic venous invasion was significantly higher than those in HCC without microscopic venous invasion (P<0.05). 1, 2, 3 cancer-free survival rates in patients with low ESM-1 expression were 61.0%, 38.0% and 19.0% respectively and those in patients with high ESM-1 expression were 43.4%, 7.0% and 0,respectively. The difference of the cancer-free survival rates between the high ESM-1 group and low ESM-1 group was significant (P<0.05). ConclusionThe expression of ESM-1 was not only correlated with the malignant behaviors including neovascularization and venous invasion, but also with the poor prognosis of HCC patients.