The reduction of PCDHGA9 expression in GC was remarkably correlated with the T stage (p < 0.001), N stage (p = 0.003), M stage (p = 0.006), UICC stage (p < 0.001), histological differentiation (p = 0.001), and tumor relapse (p = 0.001, Table 1). This evidence concerns the gene PCDHGA9 and gastric cancer.