As a gastrointestinal surgeon, when visiting outpatient clinics, I often encounter patients who take the initiative to check for tumor markers, believing that they will know if they have gastrointestinal cancer once they have checked for tumor markers. Is this true? My answer is no. Tumor marker is a very important test for tumor patients, which plays an important role in determining the severity of tumor, prognosis and review. If a patient’s tumor marker is high before surgery, drops after surgery, and then rises again after a year, it means there is a possibility of recurrence. However, the specificity of tumor markers is not high. Many tumor patients do not have elevated tumor markers, and there are also many benign diseases with elevated tumor markers. Therefore, we can’t completely rely on high or low tumor markers to determine whether a patient has a tumor or not. A high tumor marker is not necessarily a tumor; a low tumor marker is not necessarily not a tumor. We still have to rely on the clinical manifestations of the patient to determine whether the patient has a tumor or not, or whether it is necessary to exclude the tumor. For patients with suspected intestinal cancer, we can examine the patients with fecal occult blood, blood routine, colonoscopy and so on. Below we will look at the common digestive tumor markers: 1. Alpha-fetoprotein (AFP): AFP is the most sensitive and specific indicator for early diagnosis of primary liver cancer, and if the value of AFP is elevated in adult’s blood, then it means there is a possibility of liver cancer. a significant elevation of AFP is generally suggestive of primary hepatocellular carcinoma, and AFP is elevated in 70-95% of the patients, and the more advanced the stage, the higher the content of AFP is, but negative AFP does not exclude primary liver cancer. AFP levels are higher in 70-95% of patients, the more advanced the stage, but negative AFP levels do not exclude primary liver cancer. Embryonal carcinoma of gonads and endodermal sinusoidal carcinoma of ovary will also show obvious elevation of AFP. moderate elevation of AFP is also common in alcoholic cirrhosis, acute hepatitis and HBsAg carriers. Some gastric cancers are also AFP-positive, which are called AFP-positive gastric cancers and have high metastatic potential. Carcinoembryonic antigen (CEA): CEA is an important tumor-associated antigen, 70-90% of patients with colon adenocarcinoma are highly positive for CEA, and the order of positivity in other malignant tumors is gastric cancer (60-90%), pancreatic cancer (70-80%), small intestine adenocarcinoma (60-83%), lung cancer (56-80%), liver cancer (62-75%), breast cancer (40-68%), urological cancer (40-68%), and urinary tract cancer. 68%), urinary tract cancer (31-46%). 3, Cancer antigen 125 (CA125): CA125 is the first choice marker for ovarian cancer and endometrial cancer, and it is the most important index for early diagnosis, therapeutic observation, prognosis judgment, recurrence and metastasis monitoring of ovarian cancer, and the combination of CA125 measurement and pelvic examination can improve the specificity of the test. CA125 can improve the specificity of the test and the combination of pelvic examination, and it has a high diagnosis rate for fallopian tube cancer, endometrial cancer, cervical cancer, breast cancer and mesothelial cancer, while the positive rate of benign lesions is only 2%. elevated CA125 level is a signal of recurrence of female genital tumors, and it can also be seen in a variety of gynecological benign diseases, such as ovarian cysts, endometriosis, cervicitis, gastrointestinal tract cancers, cirrhosis of the liver, hepatitis, and so on. 4, Cancer antigen 19-9 (CA19-9): CA19-9 is a relevant marker for pancreatic cancer, gastric cancer, colorectal cancer, gallbladder cancer, and a large number of researches have proved that the concentration of CA19-9 is related to the size of these tumors, and it is the most sensitive marker for pancreatic cancer reported so far. The positive rate of gastric cancer, colorectal cancer, gallbladder cancer, bile duct cancer and liver cancer will also be high. 5, Carcinoma antigen 72-4 (CA72-4): CA72-4 is one of the best tumor markers for diagnosing gastric cancer, with high specificity for gastric cancer, its sensitivity can be up to 28-80%, and it can monitor more than 70% of gastric cancers if it is detected together with CA19-9 and CEA. CA72-4 also has different detection rates for other gastrointestinal cancers, breast cancer, lung cancer and ovarian cancer. CA72-4 also has different detection rates for other gastrointestinal cancers, breast cancer, lung cancer and ovarian cancer. CA242 is a new tumor-associated antigen, the level of which will increase when tumor occurs in the digestive tract. It has high sensitivity and specificity for pancreatic cancer and colorectal cancer, with 86% and 62% positive detection rate respectively, and also has certain positive detection rate for lung cancer and breast cancer. It can be used for the differential diagnosis and prognosis of pancreatic cancer and benign hepatobiliary diseases, as well as for the preoperative prognosis and recurrence identification of colorectal cancer patients.