The MSI test is used primarily to identify evidence of DNA mismatch repair defects in colorectal or endometrial cancer patients as part of Lynch syndrome screening.105 With the advent of massive parallel sequencing panels to identify germline variants in mismatch repair genes, it is likely that the MSI test will eventually be replaced by more cost-effective and direct means of testing for heritable cancer risk.106, 107, 108 For purposes of assigning molecular class of gastric cancer, MLH1 methylation testing is likely to be a suitable surrogate test. This evidence concerns the gene MLH1 and cancer.