Abstract: Objective To investigate the differential expression of S100 A9 protein in different phenotype of human hepatocellular carcinoma (HCC) tissues,and to explore the clinicopathologic significance.MethodsExpressions of S100 A9 protein in different liver tissue specimens were observed by immunohistochemistry assay. The specimens included 5 cases of normal liver,15 cases of cirrhosis caused by hepatitis B,and 48 cases of HCC that were with different phenotypes. The relativity between the results of immunohistochemistry assay and the clinicopathologic parameters were analyzed.Results S100 A9 protein localized in hepatocellular cytoplasm. Expression of S100 A9 protein in normal liver tissue and small HCC was negative. One-third cirrhosis caused by hepatitis B and 16 cases (33.3%) of HCC were S100 A9 positive. The positive expression rate of invasive HCC was higher than that of non-invasive HCC (52.17% vs.16%,P=0.019),while the positive expression rate of grade III HCC by Edmondson-Steiner classification was significantly higher than that of grade II (81.8% vs.18.9%,P=0.000).Clinicopathologic correlation study found that S100 A9 expression was closely related to HCC invasion and differentiation.ConclusionsExpression of S100 A9 protein in invasive HCC increases significantly.S100 A9 may be a potential and valuable molecular marker for HCC classification and invasion prediction.

Key words: Human hepatocellular carcinoma, S100 A9, Immunohistrochemisty assay