Types Definition of colon cancer: Cancer that forms in the tissues of the colon (the longest part of the large intestine). Most colon cancers are adenocarcinomas (cancers that begin in cells that make and release mucus and other fluids). 
Definition of rectal cancer: Cancer that forms in the tissues of the rectum (the last several inches of the large intestine before the anus).
Estimated new cases and deaths from colon and rectal cancer in the United States in 2008:
- New cases: 108,070 (colon); 40,740 (rectal)
- Deaths: 49,960 (colon and rectal combined)