Colon cancer, a malignant tumor of the large intestine, affects both men and women. It affects 2 percent to 6 percent of all men and women in their lifetime. It is the third most commonly diagnosed cancer in both sexes.
The vast majority of colon cancer cases are not hereditary. However, approximately 5 percent of individuals with colon cancer have a hereditary form. In those families, the chance of developing colon cancer is significantly higher than in the average person. Identifying those individuals and families that might be at-risk for hereditary colon and associated cancers can dramatically reduce the number of cancer diagnoses in these families.