Evidence suggests that up to 15% of CRC cases exhibit microsatellite instability (MSI), the majority of which are sporadic and mostly resulting from MMR protein deficiency, primarily caused by epigenetic silencing of the MLH1 gene via promoter hypermethylation or somatic mutations in MMR genes [53]. This evidence concerns the gene MLH1 and hyperinsulinemic hypoglycemia, familial, 4.