APC and colorectal carcinoma: This model suggests that there is a transition from normal mucosa to adenoma initially, followed by the subsequent development of invasive carcinoma and metastasis due to sequential accumulation of deleterious mutation in genes which include APC (adenomatous polyposis coli), K-ras and p53. Gene inactivation by abnormal methylation patterns is also implicated in the development of CRC [3].