Metastasis or recurrence usually occurs after breast cancer undergoes surgery and is a major feature of malignant tumors. About 1/3 of patients will develop recurrent metastases within 5-10 years after surgery, and early detection of these recurrent metastases and timely treatment are expected to prolong survival. Therefore, prevention and early diagnosis are especially important. The early stage of recurrent metastasis is often asymptomatic. Regular check-ups in hospitals (preferably in the primary care oncology hospitals) can detect some of the early signs of metastasis. Regarding the follow-up time, it is recommended to follow up every 3-4 months within 2 years after surgery, every 6 months in the 2nd-5th years, and every year after 5 years until the end of life. The specific components of follow-up visits include clinical examination by the physician, ultrasound and X-ray examinations of metastasis-prone organs and sites, as well as skeletal nuclear scans, CT and magnetic resonance imaging, as necessary. Another important part of postoperative follow-up is to check the contralateral breast, because the risk of primary breast cancer in the contralateral breast will increase 3-4 times after one side has breast cancer. In addition to incisional local chest wall recurrence and lymph node metastasis, breast cancer metastasis mainly occurs in tissues and organs with rich blood circulation. The autopsy of breast cancer patients found that 60%-80% had lung metastasis, 50%-60% had liver metastasis and 50% had bone metastasis. The time of recurrent metastasis is most common within 2 years after surgery, and the chance of recurrent metastasis decreases as the time after surgery increases, but there is no lack of cases of recurrent metastasis more than 10 years or even 20 years after surgery, therefore, breast cancer should be followed up for life after surgery. 3. Symptoms of different metastatic sites Lung metastasis Most patients with lung metastasis lack typical symptoms, only 1/3 have cough, coughing up bloody sputum, chest pain, shortness of breath and other manifestations. Chest X-ray is the simplest and easiest method. For breast cancer patients, it is recommended to check every six months to a year. For isolated lesions or lesions limited to one or one lobe of the lung, if no clear metastases are found in other parts of the body, there is still a chance for surgery and a few patients can still have long-term survival after resection. Bone metastases Bone metastases are mostly located in the vertebrae, pelvis and femur of the thigh. The main symptom is progressively increasing pain with localized pressure but often no mass can be felt. Some of them may show symptoms of nerve compression or pathological fracture. Whole-body nuclide bone imaging can diagnose bone metastases three to six months before bone destruction is detected by X-ray, thus buying time for early treatment and pain relief. Liver metastases are often asymptomatic in the early stage, and only when the tumor grows to a certain extent may symptoms such as wasting, loss of appetite, distention and pain in the liver area, weakness, low fever and jaundice appear, but they are mostly advanced at this time. Clinical follow-up often reveals relatively early liver metastasis, and about 10% of liver metastasis cases can be surgically resected. Soft tissue metastases mainly include local recurrent metastases in the chest wall, ipsilateral axillary (residual) and supraclavicular lymph nodes, and contralateral breast, axillary, and supraclavicular lymph node metastases. There are also internal breast lymph nodes adjacent to the sternum and mediastinal lymph node metastases. In some cases, limited recurrent metastases may also be cured by reoperation or local radiotherapy. Other brain metastases may manifest as headache, nausea, vomiting, blurred vision, etc.; pleural cavity metastases may present with chest pain, shortness of breath, pleural fluid, etc.