For advanced gastric cancer (AGC), even after a curative gastrectomy the disease recurs in both regional and distant sites in 30∼50% of patients. Given the high risk of relapse, seeking prognostic factors is crucial to allowing risk-adapted treatments for this disease. Evidences suggested that the biologic behavior of cancers with the DNA mismatch repair (MMR) system deficient might be distinct from that with intact MMR in histopathologic features, cancer recurrence, and survival. Therefore, we conducted this study to evaluate the clinical significances of MLH1 and MSH2 expression in AGC on varying positive criteria for immunohistochemical expression. This study included 87 consecutively selected patients with T-stage II and III AGC. We found a statistically significant difference in histological type on the positive criteria where more than 90% of cancer cells positive for MLH1 are accepted as positive. In other variables relating to prognosis such as tumor invasion, lymph node metastasis, survival, we could not find any differences in MLH1 and MSH2 expression of the cancer cells. These findings suggest that MLH1 and MSH2 expression in AGC might not related to prognosis and there might be a correlation between MLH1 expression and histological types. (Cancer Prev Res 12, 231-239, 2007)

Keywords: Stomach cancer, MLH1, MSH2, DNA mismatch repair, Prognosis, Histology