CA19-9 is clinically one of the commonly used tumor markers on. It is not specific, and lesions of multiple systems can cause abnormal CA19-9. Malignant tumors such as breast cancer, lung cancer, colorectal cancer, ovarian cancer and so on. Benign lesions such as acute and chronic pancreatitis, cholecystitis, chronic liver disease, pneumonia, ovarian cysts, etc. A decrease in CA19-9 indicates that the lesion causing the increase in CA19-9 is under control, whether it is a malignant tumor or a benign lesion, indicating that the patient’s condition is improving. Patients should also review CA19-9 values and related imaging examinations regularly after CA19-9 decreases until the condition is stable in the long term.