CTNNB1 and colorectal carcinoma: In 80 human CRC tumor specimens stratified by the presence or absence of microsatellite instability (MSI), mutations in the CTNNB1 gene were found in 53 tumor specimens (25%) with high-frequency MSI (MSI-H) but no mutations were observed in the CTNNB1 gene in the 27 MSI tumors with low-frequency MSI (MSI-L) [56].