Alpha-fetoprotein (AFP) AFP is a glycoprotein synthesized by the liver and yolk sac during the embryonic stage, and the amount in the blood circulation of normal adults is minimal <20 μg/L. AFP is the best marker for the diagnosis of primary liver cancer, with a positive diagnostic rate of 60% to 70%. The diagnosis of primary liver cancer can be made when serum AFP > 400μg/L for 4 weeks or 200-400μg/L for 8 weeks is combined with imaging examination. In patients with acute and chronic hepatitis and cirrhosis, serum AFP concentration may be increased to varying degrees, but the level is often less than 300ug/L. Germinal embryonal tumors (testicular cancer, teratoma) may have increased AFP levels. Carcinoembryonic antigen (CEA) Carcinoembryonic antigen is a glycoprotein embryonic antigen found in fetal and colon cancer tissues and is a broad-spectrum tumor marker. The normal reference value of serum CEA is <5μg/L. The positive rate of CEA in malignant tumors is colon cancer (70%), gastric cancer (60%), pancreatic cancer (55%), lung cancer (50%), breast cancer (40%), ovarian cancer (30%) and uterine cancer (30%) in order. CEA is an adhesion molecule and is an important marker of metastatic recurrence of many tumors. Cancer antigen 125 (CA125) CA125 is present in epithelial ovarian cancer tissues and patient serum and is the most studied marker of ovarian cancer, with important implications for early screening, diagnosis, treatment and prognostic applications. Other non-ovarian malignancies (cervical cancer, uterine body cancer, endometrial cancer, pancreatic cancer, lung cancer, gastric cancer, colon/rectal cancer, breast cancer) also have a certain positive rate. Benign gynecological diseases (pelvic inflammatory disease, ovarian cysts, etc.) and early pregnancy may show varying degrees of elevated serum CA125 levels. Cancer antigen 15-3 (CA15-3) CA15-3 can be used as an adjuvant diagnosis of breast cancer, postoperative follow-up and as an indicator of metastatic recurrence. It has low sensitivity (60%) for early stage breast cancer, 80% sensitivity for advanced stage, and high positive rate (80%) for metastatic breast cancer. Other malignant tumors also have a positive rate, such as: lung cancer, colon cancer, pancreatic cancer, ovarian cancer, cervical cancer, primary liver cancer, etc. Glycoantigen 19-9 (CA19-9) CA19-9 is a glycoantigen associated with gastrointestinal cancer and is usually found in the normal fetal pancreas, gallbladder, liver, intestine and normal adult pancreatic and bile duct epithelium. The detection of serum CA19-9 can be used as an auxiliary diagnostic indicator for pancreatic cancer, gallbladder cancer and other malignant tumors, and is of great significance for monitoring changes in disease and recurrence. Serum CA19-9 levels are also elevated in patients with gastric, colon/rectal, liver, breast, ovarian and lung cancers to varying degrees. CA19-9 levels are also elevated to varying degrees in certain gastrointestinal inflammatory diseases, such as acute pancreatitis, cholecystitis, cholestatic cholangitis, hepatitis, and cirrhosis of the liver. Cancer antigen 50 (CA50) CA50 is a marker for pancreatic, colon and rectal cancer, and is the most commonly used glycoantigen tumor marker, because it is widely found 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 certain organ. CA50 can be detected in various malignant tumors with different positive rates, and the positive detection rate for 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, stomach cancer, colorectal cancer and ovarian cancer. CA242 is a glycolipid antigen associated with pancreatic cancer, gastric cancer and colorectal cancer. Serum CA242 has good sensitivity (80%) and specificity (90%) for the adjuvant diagnosis of pancreatic cancer and colorectal cancer. Elevated serum CA242 levels are seen in patients with lung, liver, and ovarian cancers. CA72-4 is one of the best tumor markers for the diagnosis of gastric cancer, with high specificity and sensitivity up to 28-80%. For patients with metastasis, the positive rate of CA72-4 is much higher than that of non-metastatic patients. CA72-4 levels can rapidly decrease to normal after surgery. In 70% of recurrent cases, CA72-4 concentrations are first elevated. The main advantage of CA72-4 over other markers is its high specificity for the differential diagnosis of benign lesions, with a detection rate of only 0.7% in a large number of patients with benign gastric disease. There is also a positive rate for colon/rectal, pancreatic, liver, lung, breast and ovarian cancers. Ferritin (SF) Elevated ferritin can be seen in the following tumors: acute leukemia, Hodgkin's disease, lung cancer, colon cancer, liver cancer, and prostate cancer. Detection of ferritin has diagnostic value in metastatic liver tumors. 76% of patients with liver metastases have ferritin levels higher than 400 μg/L. When liver cancer is present, low AFP measurements can be supplemented with ferritin measurements to improve the diagnostic rate. Ferritin is also elevated in cases of hyperpigmentation, inflammation, and hepatitis. The reason for elevation may be due to cell necrosis, blocked erythropoiesis or increased synthesis in tumor tissue. Prostate-specific antigen (PSA) PSA is a glycoprotein synthesized by human prostate epithelial cells and secreted into seminal plasma. PSA is mainly found in prostate tissue and is not present in women. The level of PSA in normal male serum is low, with serum reference values <4 μg/L; PSA is organ-specific, but not tumor-specific. The positive rate for the diagnosis of prostate cancer is 80%. The serum PSA level is also elevated to varying degrees in benign prostate disease. Serum PSA measurement is a monitoring indicator for postoperative recurrence and metastasis of prostate cancer and for the observation of efficacy. It is present in the blood in two forms: bound PSA and free PSA. Prostate acid phosphatase (PAP) Elevated serum PAP in prostate cancer is an important indicator for diagnosis, staging, efficacy observation and prognosis of prostate cancer. Prostatitis and prostate enlargement PAP is also increased to some extent. β2-microglobulin (β2-MG) β2-microglobulin (β2-m) is expressed on the surface of most nucleated cells. It is mostly used clinically to diagnose lymphoproliferative diseases such as leukemia, lymphoma and multiple myeloma. Its level correlates with the number of tumor cells, growth rate, prognosis and disease activity. In addition, it can be used to stage patients with myeloma based on this level. Serum β2-MG can be increased in renal failure, inflammation and various diseases. Therefore, increased serum β2-MG should be excluded due to certain inflammatory diseases or reduced glomerular filtration. Neuron-specific enolase (NSE) NSE is an isoenzyme of enolase, which is a tumor marker for small cell lung cancer (SCLC) with a 91% positive diagnostic rate. It helps in the differential diagnosis of small cell lung cancer and non-small cell lung cancer (NSCLC). It is also valuable for the observation of the efficacy and recurrence monitoring of small cell lung cancer. Neuroblastoma, serum NSE concentration can be significantly increased in neuroendocrine cell tumors. Cytokeratin 19 (Cyfra21-1) Cyfra21-1 is a soluble fragment of cytokeratin-19. Cyfra21-1 is the preferred marker for non-small cell lung cancer, especially squamous lung cancer. Cyfra21-1 is also a good marker for breast, bladder and ovarian cancers. Squamous cell carcinoma antigen (SCCA) Squamous cell carcinoma antigen (SCCA) is a tumor-associated antigen TA-4 extracted from cervical squamous epithelial cell carcinoma tissue, with a minimal serum level of <2.5 μg/L. SCCA is a tumor marker for squamous carcinoma, and is suitable for the auxiliary diagnosis, treatment observation and recurrence monitoring of cervical, lung squamous, esophageal, head and neck, and bladder carcinomas. Nuclear Matrix Protein-22 (NMP-22) NMP- 22 (NuclearMatrixProtein-22) is a component of the cytoskeleton. It is closely related to cellular DNA replication, RNA synthesis, regulation of gene expression, and hormone binding. In bladder cancer, a large number of tumor cells apoptosis and release NMP22 into the urine, and the urinary NMP22 can be increased 25-fold. With a threshold value of 10 kU/mL, the sensitivity for bladder cancer diagnosis is 70% and the specificity is 78.5%. The sensitivity for the diagnosis of invasive bladder cancer was 100%. Alpha-L-alphalloidinase (AFU) AFU is another sensitive and specific new marker for the detection of primary hepatocellular carcinoma of the liver. Serum AFU activity is significantly higher in patients with primary hepatocellular carcinoma than in other types of diseases, including benign and malignant tumors. However, it is worth mentioning that there is some overlap between serum AFU activity measurements in some metastatic hepatocellular carcinomas, lung, breast, ovarian or uterine cancers, and even in some non-neoplastic diseases such as cirrhosis, chronic hepatitis and gastrointestinal bleeding, which are mildly elevated. The use of AFU with AFP can improve the diagnosis of primary hepatocellular carcinoma and has a complementary effect. The significance of tumor marker (TM) testing is summarized as follows: Tumor Screening Tumor screening is to look for suspicious individuals among asymptomatic people. Tumor marker testing is an effective method for primary screening of tumors. It is commonly used for screening of high-risk groups. AFP: Screening for primary liver cancer. PSA: Screening for prostate cancer in men over 50 years old. High-risk HPV : Screening for cervical cancer. CA125+Ultrasound : Screening for ovarian cancer in women over 50 years of age. Abnormally elevated tumor markers without obvious symptoms and signs need to be reviewed and followed up. If it continues to increase, the diagnosis should be confirmed in time. Diagnosis Ancillary diagnosis: The specificity of tumor markers is not strong enough to confirm the diagnosis of tumor solely based on tumor markers, but it can provide clues for further diagnosis. Differential diagnosis: Ben-Hur protein, AFP, HCG, PSA, etc. have characteristic cancer spectrum. Cannot be diagnosed locally: tumor markers lack tissue and organ specificity. Dynamic observation: progressive elevation of tumor markers has definite diagnostic significance; elevation of markers in benign disease is transient; elevation of markers in malignant tumors is persistent. The most important clinical application of tumor markers is to monitor disease and efficacy, and to monitor the efficacy and recurrence of metastasis. After surgery, chemotherapy or radiotherapy, there is a good correlation between the rise and fall of specific tumor markers and the efficacy of treatment, and the dynamic observation can reflect whether the tumor has recurrence and metastasis.