Colorectal cancer arises from the lining of the colon. It causes more deaths than any other type of cancer except lung cancer, but it is curable if detected and removed before it spreads to other organs. Fortunately, colon cancer develops from growths called polyps, which do not spread to other organs but are detectable by imaging tests, such as radiography; inspecting the surface of the colon through a flexible tube (colonoscopy); and testing the stool for substances released from polyps and cancers. Polyps take 5 to 10 years to become cancerous. Abnormalities in DNA from cells in a polyp cause the cells to lose control of division, which allows the polyp to become larger. Additional DNA abnormalities occur that allow cancer cells to invade the rest of the body. Polyps and cancer constantly shed cells into the stool, and it is possible to detect the mutations that cause polyps to grow and become malignant. The tests are called stool DNA tests.