On the other hand, colorectal cancer that occurs in patients with hereditary non-polyposis colorectal cancer (HNPCC) involves mutations in mismatch repair gene such as hMLH1 and hMSH2 and microsatellite instability (MSI), suggesting that there is not one carcinogenic route for cancer development. This evidence concerns the gene MLH1 and hereditary nonpolyposis colon cancer.