Hepatocellular carcinoma is a common malignant tumor in China, and its preferred treatment method is still surgical resection. However, not all hepatocellular carcinoma can be surgically resected, instead, only about 20% of them can be surgically resected when diagnosed. For unresectable hepatocellular carcinoma, interventional treatment can be used, which includes: hepatic artery embolization chemotherapy, percutaneous anhydrous alcohol injection (PEI), radiofrequency ablation, microwave ablation, laser ablation, freezing, trans-laparoscopic hepatectomy and so on. These methods seem to be less traumatic to the patient compared to hepatectomy, so they are now mostly called “minimally invasive”. However, we should note that the so-called minimally invasive is a relative concept, and improper methods can also have serious consequences, sometimes even life-threatening. In this lecture, we will introduce several minimally invasive treatment methods commonly used in clinical practice. I. Hepatic artery embolization chemotherapy Since 1980s, TACE has been widely used for unresectable hepatocellular carcinoma. After more than 20 years of clinical application, a lot of experience has been accumulated and the scope of its application has been expanding, and there is also a more objective understanding of its clinical application value. The blood supply of primary hepatocellular carcinoma is 95%-99% from hepatic artery. After the embolic agent is injected into hepatic artery by catheter, it can block the blood supply of tumor and reduce the blood flow of tumor by 90%, causing ischemia and necrosis of tumor to achieve the purpose of destroying tumor. Meanwhile, the infusion of anticancer drugs through hepatic artery can make the local drug concentration of tumor higher and improve the therapeutic effect. Problems: In more than 20 years of clinical application, TACE has also exposed its shortcomings and limitations, because the peripheral part of cancer nodes and envelope mainly depend on portal vein for blood supply, so TACE cannot treat patients with liver cancer radically and has a high recurrence rate in the short term,; there are many complications after TACE treatment, such as liver function damage, post-embolization syndrome (upper gastrointestinal bleeding, ectopic embolism, fever), etc. After applying TACE before resectable hepatocellular carcinoma, it may cause thickening, atrophy and adhesion of gallbladder wall and adhesion of cancer foci with diaphragm, lateral abdominal wall and omentum, which may aggravate cirrhosis of liver, prolong operation time and increase intraoperative bleeding, and increase the difficulty and danger of operation. In 1983, Nobuyuki Sugiura and others were the first to use ultrasound-guided percutaneous percutaneous intratumoral injection of anhydrous alcohol to treat hepatocellular carcinoma, and achieved good efficacy. It has developed from simple ultrasound-guided, anhydrous alcohol injection to ultrasound or CT-guided, intra-tumoral injection of multiple drugs. The main mechanisms of ethanol ablation are: 1 in tumor cells, ethanol causes cell plasma dehydration, followed by coagulative necrosis and fibrous tissue proliferation; 2 in tumor vessels, ethanol can lead to endothelial cell necrosis and platelet aggregation, therefore leading to thrombosis and tissue ischemia. The size and shape of hepatocellular carcinoma necrosis is not completely consistent from one treatment to another because of the great variation in histological characteristics, the degree of vessel formation, the presence of envelope or septum, and the different firmness of the tissue. Indications and contraindications Alcohol injection is mainly applicable to patients with tumor diameter ≤3cm and number of tumors ≤3, and the best efficacy is achieved by single nodule. It should not be used with caution for patients with gastrointestinal ulcer and alcohol allergy. Microwave ablation In 1979, Tahuse, a Japanese surgeon, first applied microwave knife for the experimental study of rabbit liver resection successfully, and then used this cutter for clinical application, which laid the experimental and clinical foundation for microwave treatment of liver cancer. The principle of microwave therapy is that it can make the target tissue molecular coupling pole is shocked and rotated to generate heat, resulting in thermal coagulation. The main mechanism of thermal denaturation of liver tissue is the rotation of water molecules, which alternates with the ultra-high speed microwave (2450 MHz) electric field. The microwave is emitted from the distal end of the electrode, producing a high temperature zone in the range of 2.0-3.0 cm, which can form a shuttle-shaped solidification foci in the liver cancer tissue. Indications for microwave therapy include inoperable hepatocellular carcinoma and those who are not suitable for chemoembolization or failed chemoembolization and ethanol therapy due to severe liver function abnormalities or low blood supply. Generally speaking, the ideal size of liver cancer for microwave ablation should be less than 3 cm in diameter and the number of tumors should be less than 4. Ultrasound-guided percutaneous microwave coagulation therapy (PMCT) is commonly used in clinical practice. Under the guidance of ultrasound, a 14-gauge needle is punctured in the cancer site, and then a microwave electrode is inserted into the cancer site through the needle, which is energized with 60w power for 120s, and a circular coagulation zone with a maximum diameter of slightly more than 2cm is produced in the tip area of the electrode. For lesions with fibrous tissue or septa, microwave ablation can also make the lesion completely coagulated and necrotic by heating, therefore, it is very effective for fibrotic liver cancer that is not sensitive to ethanol ablation or chemoembolization. The mechanism, indications, advantages and contraindications of microwave ablation are similar to those of radiofrequency ablation. Compared with radiofrequency ablation, microwave ablation takes less time (<60s) and the shape of necrosis is oval, so microwave ablation is less damaging, but larger tumors require multiple treatments.