Figure 1.

The causes of colorectal cancer. Sporadic CRC refers to those cases that occur in individuals over age 50 years without any identifiable predisposing factors. Familial cases are those with a family history of CRC but exclusive of FAP, HNPCC, and the hamartomatous polyposis syndromes. The approximate percentage of distribution for each condition is as follows: sporadic, 75%; familial, 15%; HNPCC, 5%; FAP, 1%; IBD, 1%; MAP, 1%; hamartomas, < 1%.

Key: IBD = inflammatory bowel disease; MAP = MYH-associated polyposis