The liver is the best organ for the development of hematogenous metastatic cancer. According to statistics, the occurrence of intrahepatic metastatic cancer is second only to lymph node metastasis due to the lymphatic route. During the development of malignant tumors, 25% to 50% of primary tumors metastasize to the liver. The common primary lesions of metastatic cancer in liver mainly originate from malignant gastrointestinal tumors, lung cancer, breast cancer and melanoma, and the most common one is colorectal cancer. About 35% of colon cancer patients have formed metastatic cancer in liver during the course of their disease development, and cumulatively 60% to 80% of colon cancer patients eventually have liver metastasis. I. Diagnosis of metastatic liver cancer At present, there are various modern examination and treatment methods and measures, but they all have their own advantages, disadvantages and indications. In order to avoid misdiagnosis and ineffective treatment for patients with metastatic liver cancer, and to further improve the efficacy and quality of life of patients, the German Cancer Society and the German Surgical Association have reached a consensus and made certain regulations on the principles of diagnosis and treatment of metastatic liver cancer. Most of the metastatic liver cancers are diagnosed after the primary tumor is detected and during its treatment. The significance of preoperative diagnosis is: 1. to determine whether there is local recurrence of the primary tumor; 2. to determine whether there is intrahepatic, extrahepatic or extra-abdominal tumor infiltration: 3. to determine the extent and scope of intrahepatic metastasis. The sensitivity of ultrasound in detecting liver metastases is relatively low at about 41% (38%-68%), mainly because ultrasound has difficulty in detecting smaller metastases, and the specificity of ultrasound examination is similar to other examination methods. The sensitivity of plain CT examination is about 48% (under the condition of l0mm layer thickness), and its specificity can reach 71% after doing enhancement scan, and through a series of technical improvements, its specificity can finally reach about 85% and 93%. The sensitivity depends mainly on the size of the tumor, and is 71.4%, 84.2%, 96% and 100% for lesions less than 1 cm, 1-2 cm, 2-3 cm and more than 3 cm in diameter, respectively. Enhanced CT scan with contrast injection through the superior mesenteric artery has a sensitivity of up to 81% (21%-100%) and is useful in detecting smaller lesions, although it has a false positive rate of up to 40%. Because of its low specificity (68%) and invasive nature, it is rarely used as a confirmatory test for liver metastases, but it can still be used when an enlarged partial hepatectomy is proposed in order not to miss suspicious lesions. Compared with CT, MRI has the advantage of better differentiation between hepatic hemangioma, hepatic cyst and hepatic metastatic cancer, but it has been reported in the literature that it does not show extrahepatic tumor lesions as well as CT. There is no significant difference between CT and MRI in terms of sensitivity and specificity in the diagnosis of hepatic metastatic cancer, and its sensitivity and specificity are still improving with technical improvements. Of course, it is also related to the experience and practice level of the examiner and diagnostician. Because CT is widely used and shows extrahepatic tumors more clearly, it is prescribed by the German Cancer Society as a routine test for the diagnosis of metastatic liver cancer, and MRI is recommended in certain special cases. Diagnosis of metastatic liver cancer (German Cancer Society protocol) Required tests: History and clinical examination, abdominal ultrasound, spiral CT, MRI Required tests in individual cases: Tumor markers Dissection Positron emission tomography (PET-CT) Preoperative pathology and immunohistochemistry are not necessary for patients who are to undergo surgery. However, they are useful for patients with an unclear primary focus and for non-surgical patients. Next to preoperative laparoscopy and ultrasound, the results of a survey report by the American Society for Gastrointestinal Surgery and the Endoscopy Society showed that the sensitivity of double-helical CT for the diagnosis of liver malignancies was improved by laparoscopy. Current. The exact extent to which laparoscopy before local intervention for liver metastases or intraoperative ultrasonography before surgery has an impact on the outcome of treatment is inconclusive; therefore, the German Cancer Society does not have a clear affirmation of the necessity of these two examination methods. The diagnosis of metastatic liver cancer in those cases where the primary focus is clinically unclear is sometimes difficult. If morphological examination alone is not sufficient to determine the origin of the original foci of liver metastases, immunohistochemistry is appropriate to examine and ultimately determine the origin of the primary tumor. CD30 positivity is useful in the diagnosis and differential diagnosis of large cell degenerative lymphoma, and Krüger et al. found that in this type of metastatic carcinoma, tumor necrosis and undifferentiated metastatic carcinoma are often present, and that it is particularly important to exclude metastatic carcinoma from malignant melanoma or mesenchymal tumor and infiltrative changes from malignant lymphoma. Brown et al. studied the origin of adenocarcinoma metastases based on eight primary tumor antibodies and found that when the primary tumors were breast, ovarian, lung, and gastrointestinal malignancies, the diagnosis was confirmed by four antigens (BCA225, CEA, CA125, CA199) in 66% of cases. Of course, the final determination of the primary tumor site requires a clinical diagnosis in addition to the specificity of the primary tumor antibody. This is especially important in breast cancer and ovarian cancer, where immunohistochemical markers lack specificity. Treatment of liver metastatic cancer 1.Surgery for the purpose of cure Surgical operation brings the possibility and hope of cure for patients with liver metastatic cancer. For patients with liver metastases from colorectal cancer, the unfavorable factors affecting their post-surgical treatment include: primary tumor with lymph node metastasis, appearance of extrahepatic tumor, metastasis within 12 months after primary tumor surgery, multiple tumors, metastatic cancer diameter greater than 5cm, and CEA value greater than 200ng/ml. The indications for surgery are: (1) discovery of liver metastases (2) the number of liver metastases is less than 4, or more than 4, but the tumor is small and mostly located in the periphery or limited to half of the liver, and the hepatic resection volume is less than 50%; (3) there is no metastasis in the abdominal lymph nodes; (4) the liver function can tolerate the surgery. The most important factor affecting the outcome of treatment is the presence of tumor cells in the normal tissue at the margin of the resected tumor. Incomplete surgical resection of the tumor means not only a significantly higher risk of intrahepatic recurrence, but also a poorer overall prognosis for the patient. The purpose of surgery, as with all other local treatments, is to completely destroy the metastatic cancer tissue so that no tumor cells can be seen at the surgical margins. According to the study of Cady et al. experts, it was found that when the surgical incision margin was less than 1 cm away from the tumor tissue, i.e., the surgical safety distance was less than 1 cm, the prognosis of patients was poor, so it was necessary to keep their surgical safety distance above 1 cm in any case. It can be called a perfect surgery only after complete resection of liver metastatic cancer is confirmed. Intraoperative ultrasonography with high sensitivity plays a significant role here, not only by which the images before and after surgery can be compared, but also by which palpation can be considered in order to further improve the diagnosis rate, and this method can increase the diagnosis rate of liver metastatic cancer by 20% to 30%. Regardless of intrahepatic or extrahepatic metastases, if the metastatic cancer lesions cannot be completely removed, surgical treatment is not suitable, and when there are metastases in hepatoduodenal ligament or other organs, only individual patients are suitable for surgical treatment. prognosis is worse. Surgical treatment of metastatic liver cancer is most concentrated and extensive in the treatment of metastatic liver cancer due to colorectal cancer, and partial hepatectomy is currently considered the only standard treatment option to cure metastatic liver cancer. Theoretically, for focal growth of metastatic liver cancer due to colorectal cancer, the possibility of complete resection of the lesion exists. For metastatic liver cancer from certain other primary tumors, the chance of simultaneous metastasis to other organs is quite high, most commonly to the gastrointestinal tract and pancreas via the portal route, and the patient’s prognosis is extremely poor. In addition to liver metastases from colorectal cancer, liver metastases from adrenal adenoid tumors, adrenal carcinoma, teratoma and breast cancer are also common. Neuroendocrine tumors are special in that they are difficult to cure, but symptomatic treatment and palliative surgery can significantly improve the survival rate. Surgical treatment of hepatic metastatic carcinoma mainly includes local lesion resection, lobectomy, and hemihepatectomy, mainly of liver segments, in terms of treatment methodology. Over the past 30 years, with the progressive deepening of knowledge and understanding of liver (especially in non-cirrhotic individuals) anatomy and physiology (especially the grading of liver segmental anatomy and hepatocyte proliferation capacity) and the continuous development of anesthesia techniques and surgical techniques, the integrity and safety of surgical procedures have been continuously improved. Surgeons can decide whether to use subsegmental resection or expanded partial hepatectomy depending on the ratio of the size of the primary tumor/secondary liver metastatic cancer lesion to the normal tissue volume; therefore, a so-called completely uniform and standardized protocol does not exist. Total hepatectomy with liver transplantation is not recommended, and the main risk factors of this procedure are its unclear long-term efficacy and the problems of immunosuppression and high tumor recurrence rate. 2. Chemotherapy Even after complete resection of metastatic liver cancer, intrahepatic tumor recurrence occurs in 32%-60% of cases and extrahepatic tumor recurrence in 28%-36% of cases. In a randomized comparative study, it was found that the prognosis of patients was not greatly affected by simple transhepatic chemotherapy, but the combination of local treatment and systemic chemotherapy could improve the prognosis, but the theory of adjuvant therapy after clinical resection of metastatic liver cancer (RO) surgery is not fully adequate. Adjuvant therapy for surgery for hepatic metastatic cancer (German Cancer Society, 2000) Local chemotherapy: mixed results discussed Systemic chemotherapy: lack of retrospective studies Applied only under investigational conditions The European Research and Treatment of Cancer Group (EORTC) is studying the significance and value of combined surgical and chemotherapeutic treatment of patients with hepatic metastatic cancer. Despite the proliferation of new chemotherapeutic agents. However, the efficacy of systemic chemotherapy for patients with metastatic liver cancer is very low. The sensitivity of systemic chemotherapy to liver metastases is often less than 20%, and systemic chemotherapy brings more toxicity and more complications. The efficacy of systemic chemotherapy is greatly compromised by the dose of treatment and the quality of life of patients is poor. Interventional hepatic artery catheter chemotherapy has been well established in the treatment of primary hepatocellular carcinoma that is difficult to be resected surgically. It can shrink the tumor and prolong the survival. Inoue applied iodinated oil plus adriamycin to treat 61 cases of metastatic liver cancer, 56% of the cases showed tumor shrinkage, but the one-year survival rate was only 43%. Local treatment methods According to statistics, only 5%-20% of colorectal cancer patients with liver metastases are suitable for subsurgery, which has promoted and facilitated the development of local treatment techniques for primary liver cancer and liver metastases to a certain extent and in a certain sense, which can be summarized as chemical and physical methods. Chemical: anhydrous alcohol injection Physical: low temperature: freezing High temperature: radiofrequency ablation, microwave coagulation, high functional aggregation ultrasound, etc. Two research groups took percutaneous liver puncture injection of alcohol therapy to treat liver metastases below 4-5 cm, and complete tumor necrosis could be achieved in 52% to 56% of cases, of which, most of the lesions were endocrine tumors below 2 cm. According to the relevant literature, the 3-year survival rate of patients treated by this protocol is 39%. Of course, some individual research groups have expressed doubts about the efficacy of this method, arguing that liver metastatic cancer is different from primary liver cancer in that its tumor parenchyma is harder, and it is not easy to spread evenly after injecting therapeutic substances into the tumor. In contrast, primary liver cancer tumors are not so hard and are surrounded by stronger normal liver tissues, so they are suitable for treatment by percutaneous liver puncture injection of alcohol therapy, therefore, this method is recommended for treatment of metastatic liver cancer only in individual cases. Radiofrequency therapy is based on thermal therapy, which is to kill tumor cells by using high temperature of 45℃-50 ℃, and it can be treated by percutaneous hepatic puncture or surgical route under B ultrasound guidance. In the first report of radiofrequency therapy, it showed that this method has less complications and lower recurrence rate, but when the tumor is 3 cm large, its recurrence rate can reach 10%-38%, however, B ultrasound has poor observation on the postoperative tumor However, ultrasound is poorly observed for postoperative tumor gasification. Local treatment methods also include microwave coagulation therapy and high power focused ultrasound therapy. Unlike other local therapies, cryotherapy is mainly performed under cesarean section, which is its significant disadvantage. Of course, it can also be performed simultaneously with surgical therapies. After a single treatment, a miraculous result of complete necrosis or even disappearance of the tumor is obtained in about 15% of patients. Cryotherapy under dissection is only indicated for certain tumor stages, especially when extrahepatic metastases need to be excluded. Cryotherapy is also effective in treating larger tumors and is superior to radiofrequency therapy in this regard. Metastatic liver cancer is a common and difficult clinical problem for which there is no definite and reasonable treatment. In fact, clinicians must choose the appropriate and correct treatment path according to the patient’s condition and individualized treatment principles. With the deepening of the understanding of the biological characteristics of metastatic liver cancer and the development of therapeutic tools, its 5-year survival rate has been significantly improved.