Illustration of colon cancer. The cancer develops on the colon's mucus membrane. In 70% of cases, the tumour develops in the sigmoid colon. Development of the tumour in a coloscopic view is shown on the right-hand side of the illustration. From top to bottom : - 1st stage, submucus membrane is infected - 2nd stage, the muscularis is infected - 3rd stage, the muscularis, the sub serous membrane and the nonperitonealised pericolic tissue and the perirectal tissue are infected.