They can invade and damage nearby tissues and organs. Sometimes cells from the tumor may break off and travel through the bloodstream or the lymphatic system and start tumors in other parts of the body. The colon and rectum form a long, muscular tube called the large intestine or large bowel. The colon is the upper 5 to 6 feet of the large intestine and the rectum is the last 6 to 8 inches. The large intestine, along with the esophagus, stomach, and the small intestine, are part of the body's digestive system.
Tumors can develop anywhere in the colon or rectum.
Sometimes a benign growth, called a polyp, may start to grow on the wall of the colon or rectum. Colorectal polyps should be removed because they can become cancerous. These can be easily removed in a doctor's office during a sigmoidoscopy or colonoscopy examination. If not removed, these cancer cells can spread outside of the colon or rectum to the nearby lymph nodes. These cells can also spread to other parts of the body such as the liver and lungs.