CA199, also known as glycoantigen 199, is a tumor marker, and high CA199 is commonly found in malignant tumors of the digestive system, such as pancreatic cancer, colorectal cancer, gastric cancer, hepatobiliary cancer, etc. Among them, pancreatic cancer tissues have the highest content of this indicator. CA199 is not used as a diagnostic indicator for digestive malignancies. If CA199 is high, it does not confirm the diagnosis of malignant tumor, but if the index continues to rise in diagnosed malignant tumors, it indicates that the disease is progressing, the disease is recurring or the efficacy of treatment is poor, which generally indicates a poor prognosis.