Ca199 is a tumor marker that is distributed in the epithelium of the pancreas and bile ducts of normal human beings and can be detected in the blood circulation as a gastrointestinal tumor-associated antigen. It is of reference significance for the diagnosis of pancreatic cancer, stomach cancer, liver cancer, ovarian cancer, esophageal cancer and breast cancer. However, elevated index does not necessarily mean cancer, but may also be caused by other reasons, such as pancreatitis, gallstones, cirrhosis, diabetes, renal insufficiency, etc. It should be considered together with clinical symptoms and other auxiliary test results.