Tumor Markers are chemical-based substances that reflect the presence of tumors. They are either not present in normal adult tissues but only in embryonic tissues, or their content in tumor tissues greatly exceeds that in normal tissues. Their existence or quantitative changes can suggest the nature of tumors, and help to understand tumor histogenesis, cell differentiation, and cell function, so as to help diagnosis, classification, prognosis judgment, and treatment guidance of tumors. Tumor markers can be divided into two categories 1, tumor tissue production, including: differentiation antigen; embryonic antigen (AFP, CEA); isoenzyme (NSE); hormone (HCG) tissue-specific antigen (PSA, free PSA); mucin, glycoprotein, glycolipid (CA125) oncogene and its products; polyamines, etc. 2, produced by the interaction between tumor and host, including: serum ferritin; immune complexes; acute temporal phase protein isoenzymes; interleukin receptors; tumor necrosis factor, etc. In the 1980s, monoclonal antibody recognition systems were developed to recognize tumor-specific macromolecular glycoprotein antigens (carbohydrate antigen, CA) obtained by hybridoma technology.CA is a tumor cell-associated antigen. The commonly used CA series are: CA 125 (ovarian cancer-associated antigen); CA 19-9 (pancreatic and intestinal cancer-associated antigen); CA 15-3 (breast cancer-associated antigen). CA 19-9 is a type of glycoantigen, and an increase in CA 19-9 indicates the possibility of pancreatitis, liver cirrhosis, diabetes, and gastrointestinal tumors. The standardized value of CA19-9: between 0-40 Elevated levels of CA19-9 can be seen in: 1) most patients with pancreatic cancer have significantly increased serum CA19-9 levels; 2) CA 19-9 levels are also elevated in hepatobiliary cancer, gastric cancer and colorectal cancer; 3) low concentrations and transient increases can be seen in chronic pancreatitis, gallstone disease, cirrhosis, renal insufficiency and diabetes mellitus. Clinical significance CA19-9 is a marker of pancreatic cancer and colon and rectal cancer. The critical value of positive serum CA19-9 is 37kU/L. 1. 85%-95% of patients with pancreatic cancer are positive. The concentration of CA19-9 will decrease after tumor resection, and then increase, it can indicate recurrence. 2.The positive rate of colorectal cancer, gallbladder cancer, bile duct cancer, liver cancer and gastric cancer is also high, and if CEA and AFP are detected at the same time, the positive detection rate can be further increased. 3, benign diseases such as pancreatitis and jaundice, CA19-9 concentration can also be increased, but often “transient”, and its concentration is mostly less than 120kU/L, must be distinguished. The significance of CEA, CA19-9 and CA72-4 was assessed for early detection of disease reproduction, based on retrospective evaluation of routine data in patients with colorectal cancer. They also consider the dependence of the results of these data analyses in a panel of defined patients, without evidence of disease (NED) and with disease (radar data) recurrence.