MLH1 and gastric cancer: The authors explained the imperfect correlation with interobserver variability in immunohistochemical analysis assessment, heterogeneity of biomarker expression in gastric cancer, and the presence of normally translated but non-functional MMR proteins in the setting of a missense MLH1 mutation, or rare genomic defects that result in MSI-H status with intact MMRD function, e.g., polymerase DNA ε1 mutation [20].