In the sporadic setting, more than 50% of dMMR/MSI-H GC cases arise from hypermethylation of the promoter region of MutL homolog 1 (MLH1), the most critical MMR gene, while mutations in MMR genes, including MLH1 and mutS homolog 2, are obsereved in approximately 15% of dMMR/MSI-H GC cases6. This evidence concerns the gene MLH1 and gastric cancer.