1. Blood biochemical examination. Hepatocellular carcinoma may show abnormal liver functions such as elevation of aspartate aminotransferase (AST or GOT) and glutamate aminotransferase (ALT or GPT), serum alkaline phosphatase (AKP), lactate dehydrogenase (LDH) or bilirubin, and decrease of albumin, and change of immune indexes such as subpopulation of lymphocytes. Hepatitis B surface antigen (HBsAg) positivity or “two-to-five” quantitative tests (including HBsAg, HBeAg, HBeAb, and anti-HBc) positivity and/or hepatitis C antibody positivity (anti-HCVIgG, anti-HCVst, anti-HCVns, and anti-HCVIgM) are important markers of hepatitis viral infection. HBV DNA and HCV mRNA can reflect hepatitis viral load. Tumor marker examination. Serum AFP and its isoforms are important indicators and the most specific tumor markers for diagnosing hepatocellular carcinoma, which are commonly used for liver cancer screening, early diagnosis, postoperative monitoring and follow-up in China. For AFP ≥400 μg/L for more than 1 month or ≥200 μg/L for 2 months, excluding pregnancy, gonadal embryonal carcinoma and active liver disease, hepatocellular carcinoma should be highly suspected; the key is to carry out imaging (CT/MRI) in the same period to see whether there is a characteristic hepatocellular carcinoma occupancy. There are still 30%-40% of patients with hepatocellular carcinoma who are negative for AFP, including ICC, highly differentiated and lowly differentiated HCC, or HCC with necrosis and liquefaction, in which AFP may not be increased. Therefore, AFP alone cannot diagnose all hepatocellular carcinomas. The positive rate of AFP for hepatocellular carcinoma diagnosis is generally 60%-70%, sometimes with large differences, emphasizing the need for regular testing and dynamic observation, and with the help of imaging or even ultrasound-guided puncture biopsy and other means to make a clear diagnosis. Other markers that can be used to assist in the diagnosis of HCC include a variety of serum enzymes, including r-glutamyl transpeptidase (GGT) and its isoenzymes, alpha-L-fucosidase (AFU), abnormal plasminogen (DCP), Golgi Protein 73 (GP73), 5’Nucleotide phosphodiesterase (5’NPD) isoenzymes, aldolase isoenzymes A (ALD -A) and placental glutathione S-transferase (GST), as well as abnormal plasminogen (DCP), ferritin (FT) and acid ferritin (AIF). Some HCC patients may have abnormal increase of carcinoembryonic antigen (CEA) and glycan antigen CA19-9. 3.Imaging examination. (1) Abdominal ultrasound (US) examination: because of easy operation, visualization, non-invasive and inexpensive, US examination has become the most common and important method of liver examination. This method can determine whether there are occupying lesions in the liver, suggest their nature, identify whether they are fluid or substantial occupations, clarify the exact location of the cancer foci in the liver and their relationship with important blood vessels in the liver, which can be used to guide the choice of treatment and surgery; it can help to understand the spread and infiltration of hepatocellular carcinoma in the liver as well as in the neighboring tissues and organs. It is of great reference value for the differential diagnosis of hepatocellular carcinoma from liver cysts and hepatic hemangiomas, etc. However, the sensitivity of detection and accuracy of characterization are affected by the limitations of instrumentation, anatomical site, operator’s technique and experience. Real-time US imaging (CEUS with ultrasonography) can dynamically observe the hemodynamics of the lesion, which can help to improve the qualitative diagnosis, but it can be false-positive for patients with ICC, which should be noted; whereas intraoperative US, which directly probes the surface of the liver after laparotomy, is capable of avoiding ultrasonographic attenuation and the interference of the abdominal wall and the ribs, and it can detect small intrahepatic lesions that were not detected by the preoperative imaging examination. (2) Computerized tomography (CT): at present, it is the most important imaging method for diagnosis and differential diagnosis of hepatocellular carcinoma, which is used to observe the morphology of hepatocellular carcinoma and the status of blood supply, detect, characterize and stage hepatocellular carcinoma, as well as to review hepatocellular carcinoma after treatment; CT has high resolution, especially multislice CT, which has a high scanning speed, and the whole liver can be scanned in a few seconds, which avoids respiratory artifacts; it can carry out multi-phase dynamic enhancement scanning, and the minimum scanning layer thickness can be as large as 0.5 mm. It is capable of multi-phase dynamic enhancement scanning and the minimum scanning layer thickness is 0.5mm, which significantly improves the detection rate and characterization accuracy of small lesions of hepatocellular carcinoma. Usually, under plain scanning, hepatocellular carcinoma is usually occupied by low density, with different manifestations of clear or blurred edges, and some of them have halo sign, and large hepatocellular carcinoma often has central necrosis and liquefaction; it can suggest the nature of lesions and know whether there are cancer foci in tissues and organs around the liver, which can help the localization of radiotherapy; in addition to clearly displaying the number of foci, size, morphology and enhancement characteristics of the foci, enhancement scanning can also clarify the relationship between the foci and important blood vessels, and whether there are lymph nodes in the liver portal and the abdominal cavity. In addition to clearly showing the number, size, morphology and enhancement characteristics of the lesions, enhancement scan can also clarify the relationship between the lesions and important blood vessels, the relationship between the hilar and abdominal lymph nodes, and the invasion of neighboring organs, which can provide a reliable basis for the accurate staging of the clinic and help to identify hepatic hemangiomas. (3) Magnetic resonance imaging (MRI or MR): no radioactive radiation, high tissue resolution, multi-directional and multi-sequence imaging, better than CT and US in displaying and resolving the internal tissue structural changes of hepatocellular carcinoma lesions, such as hemorrhage, necrosis, steatosis, and envelope, and better than CT in identifying benign and malignant intrahepatic space occupation, especially with hemangiomas, and it can show the branching of the portal vein and hepatic vein without enhancement; for small hepatocellular carcinoma, MRI or MR is more specific. For small hepatocellular carcinoma, MRI is superior to CT, and there is more evidence at present. In particular, the popularization and development of high field strength MR equipment has greatly accelerated the speed of MR scanning, which can complete thin-layer, multi-phase dynamic enhancement scanning like CT, fully displaying the enhancement characteristics of the lesion and improving the detection rate and characterization accuracy of the lesion. In addition, MR functional imaging techniques (e.g., diffusion-weighted imaging, perfusion-weighted imaging, and spectral analysis) and the application of hepatocyte-specific contrast agents can provide valuable supplementary information for lesion detection and characterization, which can help to further improve the sensitivity of detection and accuracy of characterization, as well as to comprehensively and accurately assess the efficacy of various local therapies. The above three important imaging techniques have their own characteristics and complementary advantages, and should be emphasized for integrated examination and comprehensive evaluation. (4) Selective hepatic arteriography (DSA): digital subtraction angiography is mostly used nowadays, which can clearly show small liver lesions and their blood supply, and at the same time can be used for treatments such as chemotherapy and iodine oil embolization. The main manifestations of hepatocellular carcinoma in DSA are: (1) tumor vascularity, which appears in the early arterial phase; (2) tumor staining, which appears in the parenchymal phase; (3) displacement, straightening and twisting of intrahepatic arteries in larger tumors; (4) intrahepatic arteries invaded by liver tumors can be jagged, bead-like or stiff; (5) arteriovenous fistulae; “pooling” or “lake-like”; (6) “lake”; (7) “lake”; (8) “lake”. Arteriovenous fistula; “pool-shaped” or “lake-shaped” contrast-filled area, and so on. The significance of DSA examination not only lies in diagnosis and differential diagnosis, but also can be used to estimate the scope of lesions before operation or treatment, especially to understand the situation of sub-nodules disseminated in the liver; it can also provide correct and objective information for the anatomical variations of vascular anatomy and anatomical relationship of important blood vessels, as well as portal infiltration, which is of great value for judging the possibility and thoroughness of surgical resection and deciding the reasonable treatment plan.DSA is an invasive traumatizing test and can be used in patients who have not been diagnosed after other tests. In addition, for resectable hepatocellular carcinoma, even if the imaging shows limited resectable hepatocellular carcinoma, some scholars advocate preoperative DSA, which may find lesions that cannot be detected by other imaging methods and clarify whether there is vascular invasion. (5) Positron emission computed tomography (PET-CT): PET-CT is a functional molecular imaging system that integrates PET and CT, which can reflect the biochemical and metabolic information of liver occupancy by PET functional imaging, and can carry out precise anatomical localization of lesions by CT morphology imaging, and at the same time, whole-body scanning can be used to understand the overall condition and assess the metastatic situation, so as to achieve the purpose of early detection of lesions. At the same time, whole-body scanning can understand the overall condition and assess the metastatic situation, so as to achieve the purpose of early detection of lesions, and at the same time can understand the size and metabolic changes of the tumor before and after treatment. However, the sensitivity and specificity of PET-CT for clinical diagnosis of hepatocellular carcinoma need to be further improved, and its application has not been popularized in most of the hospitals in China, so PET-CT is not recommended to be used as a routine examination method for diagnosis of hepatocellular carcinoma, but can be used as a supplement to other means. (6) Emission single-photon computed tomography (ECT): ECT whole-body bone imaging is helpful for the diagnosis of bone metastasis of hepatocellular carcinoma, and it can detect bone metastasis 3-6 months earlier than X-ray and CT examination. 4. Liver puncture biopsy. Percutaneous liver puncture biopsy with hollow needle or fine needle under ultrasound guidance for histological or cytological examination can obtain the basis of pathological diagnosis of hepatocellular carcinoma as well as molecular markers, which is very important for clarifying the diagnosis, pathological type, judging the condition, guiding the treatment and evaluating the prognosis, and it has been more and more adopted in recent years, but there are certain limitations and dangers as well. When liver puncture biopsy is performed, care should be taken to prevent liver bleeding and cancer cell implantation in the needle tract; contraindications are patients with obvious bleeding tendency, suffering from serious cardiopulmonary, cerebral, renal disorders and systemic failure.