Colorectal cancer is a disease in which cancer cells grow in the colon and/or rectum. The colon and the rectum are parts of the large intestine.
Cancer occurs when cells in the body divide out of control or order. If cells keep dividing, a mass of tissue, called a growth or tumor, forms. The term cancer refers to malignant tumors. They can invade nearby tissue and spread to other parts of the body. A benign tumor does not invade or spread.