Objective:To investigate the expression level of Met in human gastric cancer,and compare the effects of mouse anti-human Met monoclonal antibody Met4 with that of commercial rabbit anti-human Met polyclonal antibody C28(sc-161,Santa Cruz,USA)on detection of the formalin-treated Met protein in tissue microarrays(TMA) of human gastric cancer. Methods:Standard immunohistochemistry (IHC) method of Met4 and C28 was used to analyze the expression of Met in TMA of gastric cancer. The reactivity efficacies of Met4 and the polyclonal antibody C28 were compared. Results:The expression of Met in membrane on cytoplosm had no significant difference among various pathological stages of cancer(P > 0.05). Met exhibited a combined membranous and (or) cytoplasmic pattern stained by Met4,while analysied by C28,Met staining revealed positive signals in cytoplasm of tumor cells. The subcellular localizations of Met were disclosed differently by these two antibodies. The positive expression rate of Met detected by Met4 was significantly higher than that by C28(P < 0.05). In Met4-staining group,14 of 21 cases with Met positive expression in primary tumor exhibited Met positive expression in its lymph metastases simultaneously. The similar result was displayed in C28 group. The elevated expression of Met in primary gastric cancer may predict tumor lymphatic metastatic potential. Conclusion:Overexpression of Met in primary gastric cancer may be associated with lymphatic metastasis of tumor. Met4 can work as anuseful reagent for tumor diagnosis and targeted therapy.