As the MLH1 methylation value increased in the order of True MSS, Haplo-MSI, Low-MSI, and High MSI, the gastric cancers with lower tumor site (P = 0.0313), the synchronous gastric cancers (P = 0.0122) and the histologically differentiated types (P = 0.0052) increased (S4 Table). The gene discussed is MLH1; the disease is gastric cancer.