Colorectal cancer is the second leading cause of cancer death in U.S. men and women. It is the third most frequent cancer diagnosis. For the general population with average risk, guidelines recommend that screening tests, including the colonoscopy, start at 50 years old. During a colonoscopy, doctors examine the colon for the presence of polyps and other abnormalities and remove them. Several other screening tests exist, including CT colonography, blood tests, and stool DNA tests. The Yale Medicine Department of Pathology offers highly specialized expertise in this area. Most of the colorectal cancer cases are caught by screening colonoscopies, says Yale Medicine pathologist Joanna Gibson, MD, PhD.