The substances that are abnormal in the biochemical properties of tumor cells and their metabolism, and therefore appear qualitatively or quantitatively altered in the body fluids, exclusions and tissues of tumor patients, these are tumor markers. Tumor markers are mainly used in clinical practice for the detection of primary tumors, screening of tumor high-risk groups, differential diagnosis of benign and malignant tumors, observation and evaluation of tumor treatment effects as well as prediction of tumor recurrence and prognosis. An ideal marker should have the following characteristics 1. High sensitivity, which should be mainly produced by tumor cells and can be stably detected in cells and blood again. 2.Specific, not present in normal tissues or benign tumors. 3.It can reflect and predict the recurrence and progression of malignant tumor. 4.The concentration in blood, urine and body cavity fluid can reflect the size and scope of tumor. Especially, it can be measured when the tumor recurrence is not yet manifested clinically. Tumor markers are generally used to aid diagnosis, judge the efficacy and monitor the progress of tumor. What are the tumor markers? At present, the tumor markers commonly used in clinical practice are mainly divided into the following three categories: 1. proteins: 1. AFP: i.e. alpha-fetoprotein, normal value is 20μg/L. Clinical significance: (1) often 300μg/L in primary hepatocellular carcinoma; (2) about 10% of primary hepatocellular carcinoma are negative for AFP; (3) may be elevated in germinal gland embryonal tumor, gastric cancer and pancreatic cancer; (4) may be elevated in viral hepatitis and cirrhosis. (4) Mildly elevated in viral hepatitis and liver cirrhosis. 2.CEA: Carcinoembryonic antigen, normal value is 15μg/L. Clinical significance: (1) often 60μg/L in pancreatic cancer (90%), colon cancer (74%), lung cancer (70%) and breast cancer (60%); (2) has some diagnostic significance for gastric cancer. (3) CA125: Cancer antigen 125, normal value: 20,000 U/L for men and women over 50 years old; 40,000 U/L for women between 20 and 40 years old; Clinical significance: (1) a marker of ovarian cancer (97% increase); (2) can be increased in cervical cancer, breast cancer, pancreatic cancer, bile duct/cyst cancer, liver cancer, stomach cancer, colon cancer and lung cancer; (3) can be slightly increased in benign ovarian tumors and uterine fibroids. (3) Mildly elevated in benign ovarian tumors and uterine fibroids. 4.TPA: Tissue polypeptide antigen, normal value is 130μg/L. Clinical significance: (1) The positive rate of malignant tumor is 70%; (2) It can be used to observe the treatment effect of tumor. 5.CA15-3: Cancer antigen 15-3, normal value is 20,000 or 50,000 U/L. Clinical significance: (1) It is a marker of breast cancer, but its specificity is limited (positive rate is 30-50%); (2) It can be elevated in lung cancer, metastatic ovarian cancer and colon cancer. 6.PSA: Prostate-specific antigen, normal value is 4μg/L. Clinical significance: (1) Marker of prostate cancer (positive rate is 90%-97%); (2) Higher sensitivity and specificity than PAP (prostatic acid phosphatase); (3) May be increased in benign prostate tumor, prostate hypertrophy and prostatitis. 7.SCC: squamous cell carcinoma antigen, the normal value is 1,5μg/L. Clinical significance: (1) cervical cancer (83%), squamous lung cancer (25%-75%), esophageal cancer are mostly elevated; (2) ovarian cancer, uterine cancer and head and neck cancer can be elevated. 1.CA72-4: Cancer antigen 72-4, normal value is 6 or 7 μg/L. Clinical significance: (1) It is often elevated in gastric cancer (45%), ovarian cancer (67%), colorectal cancer (47%) and breast cancer (40%), and is a marker of gastric and ovarian cancer; (2) The specificity of combined detection with CA125 for ovarian cancer is 100%. (2) CA19-9: Cancer antigen 19-9, normal value is 30,000 or 70,000 U/L. Clinical significance: (1) It is a marker of pancreatic cancer and digestive tract tumors; especially for pancreatic cancer and biliary tract/cyst cancer, it has high specificity and sensitivity; (2) The compliance rate of combined detection with CEA for gastric cancer is 85%. Enzymes: 1. PAP: prostatic acid phosphatase, normal value is 2μg/L. Clinical significance: (1) its elevation parallels the development of prostate cancer; (2) it can be elevated in prostate hypertrophy and prostatitis. 2.NSE: neuron-specific enolase, normal value is 12,5μg/L. Clinical significance: (1) It is a marker of neuroblastoma; (2) It is often elevated in small cell lung cancer; (3) The positivity rate of non-small cell lung cancer is 10%-20%. 3. AFU: a-L-amyloidase, its normal value is 234-414μmol/L. Clinical significance: (1) often elevated in primary hepatocellular liver cancer; (2) positive rate of 93.1% in combination with AFP in primary hepatocellular liver cancer; (3) may be elevated in metastatic liver cancer, lung cancer, breast cancer, ovarian cancer and uterine cancer. Does a positive tumor marker mean cancer? A positive tumor marker found in physical examination may or may not be a malignant tumor. To confirm the diagnosis, further examination by CT, ultrasound and other methods are needed. Tumor markers are only auxiliary diagnostic indicators of tumor. At present, each tumor marker has certain false positives because specific 100% tumor markers are still not found. The factors that cause false positives are: (1) In benign diseases, such as inflammatory diseases, the expression of some tumor markers will increase. In benign liver diseases, AFP, glycoconjugate antigen (CA19-9), CEA and tumor polypeptide antigen (TPA), β2-microglobulin (β2-MG) in renal failure and glycoconjugate antigen (CA153), CA19-9 CEA and PSA levels are elevated. (2) There are some physiological changes, such as AFP, CA125, and human chorionic gonadotropin (hCG) are also elevated in pregnancy. (3) CA19-9 concentration can be increased in rheumatic diseases. In addition, PSA and prostatic acid phosphatase (PAP) values are found to increase after repeated rectal examinations, so rectal examinations should not be performed before blood collection. Take CEA screening for colon cancer as an example, due to the incidence and sensitivity, the number of false positives per 100,000 people was as high as 4,998, while only 26 patients with colon cancer were examined. Obviously, tumor markers are not suitable for screening asymptomatic people. Of course, some tumor markers can indeed be considered for screening of high-risk groups, such as AFP in hepatitis B surface antigen (HBsAg) carriers and cirrhotic patients, hCG in patients with suspected choriocapillary epithelial cell carcinoma, and calcitonin in families susceptible to medullary thyroid cancer.