Major related tumors: pancreatic cancer, bile duct cancer, colorectal cancer Other related tumors: hepatocellular carcinoma, gallbladder cancer, bile duct cancer, etc. Other influencing factors: It is also elevated in many patients with benign diseases of the digestive system, and it has been reported that nearly 10% of patients with pancreatitis have moderately elevated serum CA19-9. CA19-9 is a relevant marker for pancreatic cancer, gastric cancer, colon and rectal cancer, and gallbladder cancer. Numerous studies have demonstrated that CA19-9 concentration is related to the size of these tumors and is the most sensitive marker reported to date for pancreatic cancer. It is the most sensitive marker reported to date for pancreatic cancer. 85%-95% of patients with pancreatic cancer are positive, and CA19-9 measurement helps in the differential diagnosis and disease monitoring of pancreatic cancer. When CA19-9 is less than 1000 U/ml, it has some surgical significance. CA19-9 concentration will decrease after tumor removal, and if it rises again, it can indicate recurrence. There is also a high positive rate for the diagnosis of pancreatic cancer metastasis. When the serum CA19-9 level is higher than 10,000 U/ml, peripheral metastasis almost always exists. The positive rate of gastric cancer, colorectal cancer, gallbladder cancer, bile duct cancer and liver cancer will also be high, and the positive detection rate can be further improved if CEA and AFP are tested simultaneously (for gastric cancer, a combined test of CA72-4 and CEA is recommended). The concentration of CA19-9 can also be increased in benign and inflammatory lesions of the gastrointestinal tract and liver, such as pancreatitis, mild biliary depression and jaundice, but it is often “transient” and the concentration is mostly below 120 U/ml, so it must be differentiated.