Breast cancer itself is a systemic disease and metastasis, like all malignant tumors, can be through lymph node metastasis, which is called lymph node metastasis, to the lymph nodes in the axilla, supraclavicular, and retrosternal regions; it can also be through hematologic metastasis, which is metastasis to important organs, such as lung, liver, brain, and different parts of the bone; it can be through direct implantation in the region, such as satellite nodes around the tumor. Different types of breast cancer can have different metastases, for example, Luminal type breast cancer is prone to bone metastasis, HER-2 type breast cancer has a higher risk of brain metastasis, and triple negative breast cancer has a higher risk of lung and brain metastasis, so in clinical practice, we also often encounter patients who go to the clinic with distant metastasis and are found to have the primary site of breast cancer in the breast.