Post-operative follow-up should never be lax. It is very important to follow up after breast cancer surgery. Because breast cancer is a systemic disease, although it has a better prognosis compared with other malignant tumors and the current level of comprehensive treatment has been improved, about 1/3 of patients will have recurrence and metastasis within 5-10 years after surgery, and early detection of recurrence and metastasis and timely treatment are expected to prolong the survival of patients. In the early stage of breast cancer recurrence and metastasis, patients often do not have any symptoms, and early signs of metastasis can be detected by regular check-ups in hospitals (preferably in primary care oncology hospitals). In general, recurrence and metastasis are most common within two years after surgery, and the probability of recurrence and metastasis will gradually decrease as the time after surgery increases, but there are many patients who have recurrence and metastasis more than ten or even two years after surgery. After five years, the patient should be examined once a year for life. The follow-up examinations include clinical examination, ultrasound and X-ray examination of metastasis-prone organs and sites, as well as skeletal nuclear scan, CT and magnetic resonance imaging (MRI) examination, if necessary. Another important part of follow-up is to check the contralateral breast, because the risk of primary breast cancer in the contralateral breast will increase 3 to 4 times after breast cancer in one side. Breast cancer recurrence can occur in the form of local chest wall and lymph node metastasis from the surgical incision, in addition to the blood to the lung, bone, liver, soft tissue and brain. The symptoms and treatment methods are different for different metastatic sites. Most patients with lung metastasis lack typical symptoms, only 1/3 may have cough, hemoptysis, chest pain, shortness of breath, etc. Chest X-ray is the simplest and easiest method. Breast cancer patients should be examined once every six months to a year. Chest CT and MRI can also detect more minute lesions, but are not routinely used. For patients with isolated lesions or lesions limited to one lung or one lobe and no clear metastases found in other parts of the body, surgical resection can be performed and some patients can still survive for a long time after surgery. Bone metastasesBone metastases are mostly located in the vertebrae, pelvis and femur. The main symptoms are gradually worsening, well-localized pain, and localized pressure pain but often no palpable mass. Some may present with nerve compression or pathologic fractures. Bone destruction can be detected 3 to 6 months earlier by whole-body nuclide bone imaging than by X-ray, so this method can be used to diagnose bone metastases early and buy time for early treatment and pain relief. The treatment after the diagnosis of bone metastasis mainly includes bisphosphonate drugs to reduce bone destruction, local radiotherapy and systemic anti-cancer and analgesic treatment.