An abnormal growth of cells in the colon or rectum. The growth of cells is called a malignant tumor. The colon and rectum are sections of the large intestine, also called the large bowel. The colon is the first part of the large bowel. The rectum is the last few inches of the large bowel. The rectum is at the end of the colon and just above the anus.
It is important to diagnose and treat colon or rectal cancer as soon as possible. If not treated, the cancer can spread through the bowel wall to lymph nodes and the bloodstream and to other parts of the body. The large intestine is one of the 4 most common sites for cancer to occur. Another term for this type of cancer is colorectal cancer.