Abstract: Objective: To investigate the expressions of spleen tyrosine kinase protein (Syk) and the epidermal growth factor receptor 2 (HER2) protein in gastric cancer, and their correlation with the occurrence and development of gastric cancer. Methods: The expressions of Syk and HER2 protein were detected by immunohistochemical method in 55 samples of gastric cancer and 20 samples of cancer adjacent tissue. The different histological types, TNM staging, lymph node metastasis, serous infiltration, distant metastasis and expressions of Syk and HER2 proteins in stomach cancer tissue were analyzed. Results: The expressions of Syk and HER2 proteins were 21.8% (12/55) and 29.1% (16/55) in 55 patients with gastric cancer respectively. The expressions of Syk and HER2 proteins were 85.0% (17/20) and 0 in 20 samples of cancer adjacent tissue. There was a lower expression level of Syk protein in samples of gastric cancer than that of cancer adjacent tissue (P<0.01), but the expression level of HER2 protein was higher in samples of gastric cancer than that of cancer adjacent tissue (P<0.01). There were significant differences in expressions of Syk and HER2 proteins between different histological stages, TNM staging, lymph node metastasis, serous infiltration, distant metastasis (P<0.05), but there was no significant difference between age and gender. The more poor differentiation and deep infiltrating appear the more lymph node metastasis and distant metastasis, higher TNM stages and higher HER2 positive expression were. There was no Syk protein expression in the low differentiation of gastric cancer. Conclusion: Detection of Syk and HER2 protein expression can be used to assess the malignant biological behavior and the prognosis of gastric cancer, providing a theoretical target for therapy of gastric cancer.

Key words: Gastric cancer, Spleen tyrosine kinase, Human Epidermal growth factor receptor2, Immunohistochemistry