The colon , the lower part of the digestive system, processes waste products and prepares feces (stool) for elimination (a bowel movement). The inner surface of the colon can have abnormal growths, both benign and malignant (cancer). Benign growths are called polyps or adenomas. Polyps, if left undetected, can become cancerous, although not all polyps will. Colon polyps usually do not cause symptoms, so persons with polyps do not know they have them until found during a colonoscopy (see below) or other testing. If precancerous polyps are detected and removed, many cancers can be prevented. Doctors who specialize in treatment of digestive diseases, including colon polyps and colon cancer, are called gastroenterologists . Because colon cancer is the second leading cause of cancer-related deaths in developed nations, it is important to screen as many individuals as possible for the presence of colon polyps and colon cancer. The September 24, 2008, issue of JAMA includes an article about colon polyps and colon cancer screening.