The Cancer Genome Atlas project, utilizing extensive genomic and transcriptomic characterization of colorectal cancer, has proposed the classification of CRC into two major groups: tumors with microsatellite instability (MSI) and tumors with chromosomal instability.3 Cancers with microsatellite instability largely result from defective DNA mismatch repair caused by inactivating mutations or epigenetic silencing of mismatch repair genes such as the MLH1 tumor suppressor gene. This evidence concerns the gene MLH1 and cancer.