The three CpG sites showing the most significant difference in methylation level between H and L tumors were located in SEZ6L, FLT4 and ALK. Interestingly, the four most significant KEGG pathways identified by the differentially methylated genes between tumor and tumor-adjacent gastric tissues were also identified by the differentially methylated genes between H and L tumors (Table 1). This evidence concerns the gene ALK and neoplasm.