The auxiliary examinations for liver cancer mainly include serum tumor markers and imaging examinations. Serum fetoprotein and its heteroplasm Serum fetoprotein and its heteroplasm is an important index and the most specific tumor marker for the diagnosis of hepatocellular carcinoma, which is commonly used in China for the screening, early diagnosis, postoperative monitoring and follow-up of liver cancer. For AFP ≥ 400 μg/L for more than 1 month, or ≥ 200 μg/L for 2 months, pregnancy, germinal gland embryonal carcinoma and active liver disease are excluded, and liver cancer should be highly suspected. There are still 30%-40% of liver cancer patients with negative AFP test, including ICC, highly differentiated and hypofractionated HCC, or HCC with necrosis and liquefaction, AFP may not be increased. Therefore, AFP alone cannot diagnose all hepatocellular carcinoma, and the positive rate of AFP for hepatocellular carcinoma diagnosis is generally 60%-70%, sometimes it varies greatly, so regular testing and dynamic observation are needed, and imaging examination or even ultrasound-guided puncture biopsy should be used for clear diagnosis. Imaging examination is the main auxiliary means to diagnose liver cancer, among which abdominal MRI and enhanced CT are the most accurate and practical. (1) Abdominal ultrasound (US) examination: US examination has become the most common and important method for liver examination because of its easy operation, intuition, non-invasiveness and low cost. It can determine whether there are occupying lesions in the liver, suggest their nature, identify whether they are fluid or substantial occupations, clarify the specific location of cancer foci in the liver and their relationship with important blood vessels in the liver, so as to guide the selection of treatment methods and surgery; it can help to understand the spread and infiltration of liver cancer in the liver and adjacent tissues and organs. It is of great reference value for the differential diagnosis of hepatocellular carcinoma and liver cysts, hepatic hemangioma and other diseases, but its sensitivity and qualitative accuracy are somewhat affected by the limitations of instrumentation, anatomical location, operator’s technique and experience. Real-time US imaging (ultrasonography CEUS) can dynamically observe the hemodynamic situation of the lesion and help improve the qualitative diagnosis, but it can be false positive for patients with ICC and should be noted; while intraoperative US probes directly from the surface of the liver after opening, which can avoid ultrasound attenuation and interference from the abdominal wall and ribs, and can detect small intrahepatic lesions that are not detected by preoperative imaging. (2) Computed tomography (CT): It is the most important imaging method for diagnosis and differential diagnosis of hepatocellular carcinoma, and is used to observe the morphology and blood supply of hepatocellular carcinoma, to detect, characterize and stage hepatocellular carcinoma, and to review hepatocellular carcinoma after treatment. The minimum layer thickness is 0.5mm, which significantly improves the detection rate and qualitative accuracy of small lesions of liver cancer. Usually, under plain scan, most hepatocellular carcinomas are low-density occupants with clear or blurred edges, and some of them have halo signs, and large hepatocellular carcinomas often have central necrosis and liquefaction; it can indicate the nature of lesions and understand whether there are cancer foci in the surrounding tissues and organs of the liver, which can help the localization of radiotherapy. The imaging of HCC is typical in the arterial phase with significant enhancement, and in the venous phase with less enhancement than the surrounding liver tissue, while in the delayed phase the contrast continues to fade, therefore, it has high specificity. (3) Magnetic resonance imaging (MRI or MR): no radioactive radiation, high tissue resolution, multi-directional and multi-sequence imaging, superior to CT and US in terms of display and resolution of tissue structural changes inside the hepatocellular carcinoma lesion, such as hemorrhagic necrosis, steatosis and envelope. For small hepatocellular carcinoma, MRI is superior to CT, and there is more evidence. In particular, the increasing popularity and development of high-field strength MR equipment has greatly accelerated the speed of MR scanning, which can be completed with the same thin layer and multi-phase dynamic enhancement scan as CT, fully displaying the enhancement characteristics of the lesion and improving the detection rate and qualitative accuracy of the lesion. In addition, MR functional imaging techniques (such as diffusion-weighted imaging, perfusion-weighted imaging, and spectral analysis) and the application of hepatocyte-specific contrast agents can provide valuable additional information for lesion detection and characterization, which can further improve the sensitivity and accuracy of hepatocellular carcinoma detection and characterization, as well as the comprehensive and accurate assessment of the efficacy of various local treatments. The above three important imaging techniques have their own characteristics and complementary advantages, and should be emphasized for comprehensive examination and overall assessment. (4) Selective hepatic arteriography (DSA): Currently, digital subtraction angiography is mostly used to clearly show small lesions in the liver and their blood supply, while chemotherapy and iodine oil embolization can be performed. The main manifestations of hepatocellular carcinoma in DSA are: ① tumor vessels, which appear in the early arterial phase; ② tumor staining, which appears in the parenchymal phase; ③ larger tumors can be seen as displacement, straightening and twisting of intrahepatic arteries; ④ intrahepatic arteries invaded by hepatoma can be jagged, beaded or stiff; ⑤ arteriovenous fistula; “pool” or (5) arteriovenous fistula; “pool” or “lake” contrast-filled area, etc. The significance of DSA examination not only lies in the diagnosis and differential diagnosis, but also can be used to estimate the extent of the lesion before surgery or treatment, especially to understand the situation of disseminated sub-nodules in the liver; it can also provide correct and objective information on the anatomical variation of vessels and the anatomical relationship of important vessels as well as portal vein infiltration, which is of great value in judging the possibility and completeness of surgical resection and deciding on a reasonable treatment plan. DSA is an invasive DSA is an invasive test and can be used for patients whose diagnosis cannot be confirmed after other tests. In addition, for resectable hepatocellular carcinoma, even if the imaging shows limited resectable hepatocellular carcinoma, some scholars advocate preoperative DSA, which has the potential to detect lesions that cannot be detected by other imaging means and clarify the presence of vascular invasion. (5) Positron emission computed tomography (PET-CT): PET-CT is a functional molecular imaging system integrating PET and CT, which can reflect the biochemical and metabolic information of liver occupancy by PET functional imaging and precisely anatomical localization of lesions by CT morphological imaging, and simultaneous whole-body scanning can understand the overall condition and evaluate the metastasis to achieve early detection of lesions. The purpose of early detection of lesions can be achieved, and the size and metabolic changes before and after tumor treatment can be understood. However, the sensitivity and specificity of PET-CT for clinical diagnosis of liver cancer need to be further improved, and it is not yet commonly used in most hospitals in China. (6) Emission single-photon computed tomography (ECT): ECT whole-body bone imaging is helpful for the diagnosis of bone metastasis of liver cancer and can detect bone metastasis 3-6 months earlier than X-ray and CT examination. 3.Liver aspiration biopsy . Core biopsy or fine needle aspiration (FNA) can be performed under ultrasound-guided percutaneous liver aspiration to obtain the pathological diagnosis of hepatocellular carcinoma and molecular markers, which are very important for definite diagnosis, pathological type, judgment of disease, guidance of treatment and prognosis assessment. It is very important for definite diagnosis, pathological type, judgment, treatment and prognosis, and has been increasingly used in recent years, but it also has certain limitations and risks. When performing liver aspiration biopsy, care should be taken to prevent liver bleeding and needle tract cancer cell implantation; contraindications are patients with significant bleeding tendency, severe cardiopulmonary, cerebral and renal disorders and systemic failure.