Major related tumors: pancreatic cancer, stomach, colon cancer. Other related tumors: liver cancer, esophageal cancer, lung cancer. Other influencing factors: It is elevated in patients with benign gastrointestinal diseases such as pancreatic cancer, hepatitis, and cirrhosis of the liver. CA242 is a new tumor-associated antigen whose level is elevated when tumors occur in the gastrointestinal tract. It has high sensitivity and specificity for pancreatic cancer and colorectal cancer, with positive detection rates of 86% and 62%, respectively, and also for lung cancer and breast cancer. It is used for the differential diagnosis and prognosis of pancreatic cancer and benign hepatobiliary disease, and also for the preoperative prognosis and recurrence identification of colorectal cancer patients. The combination of CEA and CA242 can improve the sensitivity, compared with CEA alone, it can increase 40-70% for colon cancer and 47-62% for rectal cancer.