Tumor Marker (TM), also known as tumor marker, mainly refers to substances that are characteristically present in malignant tumor cells, or produced by abnormalities in malignant tumor cells, or produced by the host in response to tumor stimulation, and can reflect tumor occurrence and development and monitor tumor response to treatment. It exists in the tissues, body fluids and excreta of tumor patients and can be detected by immunological, biological and chemical methods. They are of great practical value in tumor screening, diagnosis, prognosis and regression, evaluation of therapeutic efficacy and follow-up observation of high-risk groups. There are various tumor markers used for clinical diagnosis, mainly six categories: carcinoembryonic antigens, enzymes, hormones, glycoproteins, oncogenes and cell surface tumor antigens. The first four categories are called serum tumor markers and the last two categories are called cellular tumor markers, which are mostly available for clinical testing at present. Serum tumor markers are one of the most commonly used clinical tests for tumor detection, which can assist in detecting early tumors, helping clinical diagnosis, staging, guiding treatment and judging efficacy, and monitoring tumor recurrence or metastasis. Alpha-fetoprotein (AFP) is the best marker for the diagnosis of primary liver cancer, with a positive diagnostic rate of 60% to 70%. It has been widely used in the screening, diagnosis, judgment of treatment effect and evaluation of primary liver cancer. Serum AFP concentration is usually positively correlated with the size of hepatocellular carcinoma. Based on the exclusion of germinal germ tumor, pregnancy and active liver disease, the criteria for diagnosing hepatocellular carcinoma by serum AFP test: ①AFP>;500μg/L for more than 4 weeks; ②AFP>;200μg/L for more than 8 weeks; ③AFP gradually increases from low concentration without decreasing. Note that ① in germline embryoma, a few metastatic tumors and pregnancy, active liver disease, liver cirrhosis inflammatory phase can be low-level elevation of serum AFP, but mostly not more than 300ug/L; ② some patients with chronic liver disease, AFP is low-level elevation, often preceded by a significant increase in serum ALT, AFP is synchronized, but generally in 1-2 months with the improvement of the disease, ALT decreases, AFP However, usually within 1-2 months, as the disease improves, ALT decreases and AFP decreases accordingly. If AFP is low (50-200 μg/L) for more than 2 months or longer and ALT is normal, one should be especially alert to the possibility of subclinical hepatocellular carcinoma. AFP heteroplasm is actually the AFP-L3 bound to LCA or PSA, and the dynamic curve of serum AFP heteroplasm activity is of great importance in judging the effect of liver cancer treatment, estimating prognosis and predicting recurrence. AFP heteroplasm is not affected by AFP concentration, tumor size and early stage of disease, and simultaneous measurement of AFP heteroplasm and AFP can improve the diagnosis of primary liver cancer. In general, LCA-conjugated AFP ≥ 25% is considered to be more likely for primary hepatocellular carcinoma, and vice versa for benign liver disease. Notably, there is some overlap between serum AFP heteroplasm in certain metastatic liver cancers, lung cancers, breast cancers, ovarian or uterine cancers, and even elevated in certain non-neoplastic disorders such as cirrhosis, chronic hepatitis and gastrointestinal bleeding. Carcino-embryonic antigen (CEA) is a broad-spectrum tumor marker and an important marker of metastasis and recurrence of many tumors, and a significant increase in CEA is often indicative of GI tumors. Among malignant tumors, the positive rate of CEA 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. However, CEA levels are also elevated to varying degrees in patients with smoking, pregnancy, some benign tumors, inflammation, cirrhosis, and degenerative diseases, but to a much lesser extent than in malignant tumors. In addition, serum CEA can be used as a basis for differentiating benign from malignant tumors. Cancer antigen 50 (CA50) is the most commonly used glycoantigen tumor marker. CA50 can be detected in various malignant tumors with different positive rates, with the first positive rate for pancreatic cancer and gallbladder cancer (94.4%), followed by liver cancer (88%), ovarian and uterine cancer (88%) and malignant pleural fluid (80%). Therefore, it can be used for the auxiliary diagnosis and prognosis monitoring of pancreatic cancer, gallbladder cancer, liver cancer, etc. It also has high value for the diagnosis of gastric cancer, colorectal cancer and ovarian tumor. However, CA50 can also be elevated in ulcerative colitis, liver cirrhosis, melanoma, etc. Cancer antigen 19-9 CA19-9 has a high positive rate in malignant tumors such as pancreatic cancer, gallbladder (ductal) cancer and liver cancer, with pancreatic cancer being the highest, so CA19-9 is a better marker for pancreatic cancer. CA199 can be a reliable indicator for clinical staging, assessment of prognosis and monitoring of recurrence or metastasis. Cancer antigen 242 CA242 is a glycolipid antigen associated with pancreatic cancer, colorectal cancer and other malignant tumors. Serum CA242 has good sensitivity (80%;) and specificity (90%;) for the adjuvant diagnosis of pancreatic cancer and other cancers. It can be elevated to varying degrees in patients with hepatocellular carcinoma, lung cancer, ovarian cancer, etc. Some other commonly used tumor markers, such as CA72-4, CA125, CAl5-3, etc. are elevated to varying degrees in liver cancer, gallbladder cancer, bile duct cancer and pancreatic cancer, but their positive rates are not as high as the above tumor markers.