There are two ways to screen for cancer, as follows: first, to check blood tumor markers, such as carcinoembryonic antigen and CA199 for digestive tract tumors, CA125 for ovarian tumors, and AFP for primary liver cancer screening, which are very helpful. If there is significant elevation, CT scan plus enhancement of upper abdomen, CT of whole abdomen and ultrasound should be done to find out whether there is tumor in the corresponding area, or gastroscopy or colonoscopy to rule out stomach cancer or intestinal cancer. colonoscopy to find out whether there is tumor or not. Therefore how to find out whether there is cancer or not is to do two main tests, one is tumor marker and the other is imaging as well as pathological examination.