CA19-9 is a glycoprotein-based tumor marker. Although it is a tumor marker, it is also present in small amounts in the pancreas and gallbladder in adults, so if CA19-9 is within the normal range or slightly higher than normal, it is generally not a problem. However, if CA19-9 is significantly higher than the normal value, the possibility of malignant tumors in the body should be highly suspected. significantly higher CA19-9 is often seen in pancreatic cancer, gallbladder cancer, bile duct cancer, gastric cancer, colorectal cancer and other malignant tumors, so corresponding tests should be done for the above tumors to find out where the tumors occur in the body, so that targeted treatment can be carried out.