The rectum is a 5-inch structure located at the end of the colon. The rectum is usually empty except when stool is propelled by the upper colon into the rectum just prior to a bowel movement.
Rectal cancer is cancerous tissue that grows along and invades the wall of the rectum. Rectal cancer and colon cancer are very similar and share many common features. The difference in location creates important differences in how each is treated. Rectal cancer, like colon cancer, may start as a polyp that becomes cancerous.