AIM: To investigate DNA ploidy and expression of MMP-9, TIMP-2, and E-cadherin in gastric carcinoma and to explore the mechanism of invasion and metastasis of gastric carcinoma. METHODS: Immunohistochemical methods were used to detect the expressions of MMP-9, TIMP-2, and E-cadherin in 156 cases, including 99 cases of gastric carcinoma, 16 cases of adjacent noncancerous mucosa, 16 cases of distant metastases and 25 cases of metastatic lymph node (LN) from gastric carcinoma. Flow cytometry DNA ploidy and S-phase fraction (SPF) analysis were performed on 57 cases, including 47 cases of gastric cancer, 6 cases of adjacent noncancerous mucosa, and 4 cases of distant metastatic cancer. RESULTS: The expression of MMP-9 was significantly correlated with Lauren’s classification, Borrmann’s classification, LN metastasis, tumor metastasis, and TNM stage, as well as depth of invasion (all P<0.05). The positive rate was lower in noncarcinoma than in carcinoma (31.3% vs66.7%, P<0.01). The expression of TIMP-2 was significantly correlated with Borrmann’s classification, LN metastasis, and the depth of invasion (all P<0.05), The expression of E-cadherin was significantly correlated with differentiation, Lauren’s classification, Borrmann’s classification, and LN metastasis, as well as the depth of invasion (P<0,01 or P<0.05). E-cadherin was less expressed in carcinoma than in noncarcinoma (42.4% vs87.5%, P<0.01). There was a positive correlation between MMP-9 and TIMP-2 and a negative correlation between MMP-9 and E-cadherin, but no correlation between TIMP-2 and E-cadherin. Also there was a positive correlation between DNA aneuploid rate and differentiation and LN metastasis. SPF that was higher than 15% was positively correlated with tumor size, differentiation and LN metastasis. And there was a significant difference between carcinoma and noncarcinoma in DNA aneuploid rate and SPF. CONCLUSION: With tumor progression and development of heterogeneity, the abnormal expressions of MMP-9, TIMP-2, and E-cadherin or DNA aneuploid rate or high SPF gradually increases, suggesting that they play a crucial role in gastric carcinoma progression. AIM: To investigate DNA ploidy and expression of MMP-9, TIMP-2, and E-cadherin in gastric carcinoma and to explore the mechanism of invasion and metastasis of gastric carcinoma. METHODS: Immunohistochemical methods were used to detect the expressions of MMP- 9, TIMP-2, and E-cadherin in 156 cases, including 99 cases of gastric carcinoma, 16 cases of adjacent noncancerous mucosa, 16 cases of distant metastases and 25 cases of metastatic lymph node (LN) from gastric carcinoma. ploidy and S-phase fraction (SPF) analysis were performed on 57 cases, including 47 cases of gastric cancer, 6 cases of adjacent noncancerous mucosa, and 4 cases of distant metastatic cancer. RESULTS: The expression of MMP- Lauren’s classification, Borrmann’s classification, LN metastasis, tumor metastasis, and TNM stage, as well as depth of invasion (all P <0.05). The positive rate was lower in noncarcinoma than in carcinoma (31.3% vs 66.7%, P <0.01 The expressio n of TIMP-2 was significantly correlated with Borrmann’s classification, LN metastasis, and the depth of invasion (all P <0.05), The expression of E-cadherin was significantly correlated with differentiation, Lauren’s classification, Borrmann’s classification, and LN metastasis, as There was a positive correlation between MMP-2 and MMP-2 in well-to-deep-invasion (P <0.01 or P <0.05) 9 and TIMP-2 and a negative correlation between MMP-9 and E-cadherin, but no correlation between TIMP-2 and E-cadherin. There was a positive correlation between DNA aneuploid rate and differentiation and LN metastasis. SPF that was higher And there was a significant difference between carcinoma and noncarcinoma in DNA aneuploid rate and SPF. CONCLUSION: With tumor progression and development of heterogeneity, the abnormal expressions of MMP-9, TIMP-2, and E-cadherin or DNA aneuploid rate or high SPF incremental increases, suggesting that they play a crucial role in gastric carcinoma progression.