Major related tumors: markers for pancreatic and colon and rectal cancers. Other related tumors: gastric cancer, gallbladder cancer, liver cancer, lung cancer, breast cancer. Other influencing factors: CA50 is also elevated at the onset of atrophic gastritis, pancreatitis, colitis and pneumonia. CA50: The antigenic determinant cluster is sialic acid Lea blood group substance with sialic acid-N-tetraoxynucleamide. Normal human serum concentration is less than 20 U/ml. CA50 is generally considered to be a marker of pancreatic and colon and rectal cancer. CA50 is a marker of pancreatic and colorectal cancer and is the most commonly used glycoantigen tumor marker, because it is widely present in the pancreas, gallbladder, liver, stomach, colorectum, bladder, and uterus, and its tumor recognition spectrum is broader than CA19-9, so it is also a universal tumor marker-related antigen, rather than a tumor marker specific to a particular organ. CA50 can be detected in a variety of malignancies with different The positive rate of CA50 can be detected in a variety of malignant tumors, and the positive detection rate of pancreatic cancer and gallbladder cancer is the first, accounting for 94.4%; the others are liver cancer (88%), ovarian and uterine cancer (88%) and malignant pleural fluid (80%). It can be used for the early diagnosis of pancreatic cancer, gallbladder cancer and other tumors, and also has high value for the diagnosis of liver cancer, gastric cancer, colorectal cancer and ovarian cancer. It is worth pointing out that CA50 is positive in 80% of AFP-negative hepatocellular carcinoma, and it is also more correct as an indicator of the thoroughness of surgical treatment. In addition, CA50 has a high positive detection rate for malignant pleural fluid, while there are no positive reports for benign pleural fluid, so CA50 testing is also of great value for differentiating benign and malignant pleural fluid. It has also been reported that the concentration of CA50 in gastric juice of patients with atrophic gastritis is significantly altered compared to normal subjects. It is usually considered that atrophic gastritis is a pre-cancerous high-risk stage, so CA50 can be used as one of the pre-cancerous diagnostic indicators. CA50 is also elevated at the onset of pancreatitis, colitis and pneumonia, but decreases with the resolution of inflammation.