Pie chart showing the fractions of colon cancer cases that arise in various family risk settings. The majority of colon cancer cases diagnosed in these settings are sporadic. The remaining cancer cases are: cases with familial risk (10%–30%); Lynch syndrome (hereditary nonpolyposis colorectal cancer) (2%–3%); familial adenomatous polyposis (<1%); and hamartomatous polyposis syndrome  (<0.1%).
Figure 1. The fractions of colon cancer cases that arise in various family risk settings. Reprinted from Gastroenterology, Vol. 119, No. 3, Randall W. Burt, Colon Cancer Screening, Pages 837-853, Copyright (2000), with permission from Elsevier.