Cancer that begins in the colon is called colon cancer, and cancer that begins in the rectum is called rectal cancer. Cancer that starts in either of these organs may also be called colorectal cancer.
The digestive system is made up of the esophagus, stomach, and the small and large intestines. The first 6 feet of the large intestine are called the large bowel or colon. The last 6 inches are the rectum and the anal canal.
SEER Cancer Stat Facts: Colon and Rectum Cancer. National Cancer Institute. Bethesda, MD, http://seer.cancer.gov/statfacts/html/colorect.html