APC and colorectal carcinoma: According to the Fearon and Vogelstein model of carcinogenesis, the accumulation of multiple mutations is required for the transformation of normal colonic mucosa into dysplastic adenomas and then into invasive carcinomas.4 CRC can be classified broadly as exhibiting either chromosomal instability through gain-of-function mutations (APC/β-catenin pathway) or microsatellite instability (MSI) (defects in DNA MMR).