Dr. Leon Yoder: The diagnosis of colon cancer is made principally by doing a colonoscopy. That's a scope that's inserted into the rectum, looking all the way around your colon, which is about four feet long, and then looking very carefully to see if there's any places that look abnormal, like a polyp growth or a mass itself. That mass will be biopsied. That biopsy will then be seen by the pathologist, who will give us a diagnosis of cancer and also the type of cancer. After we look at that cancer, if the cancer is down in the rectal area, we follow that with an endoscopic ultrasound, so we can stage the tumor and thereby, if we stage the tumor, then we know exactly how to treat right off.