The lymphatic network of the breast is very rich, and the main drainage pathways of lymphatic fluid are as follows: 1. Most of the lymphatic fluid of the breast flows to the axillary lymph nodes through the lymphatic vessels of the lateral margin of the pectoralis major muscle, and then to the subclavian lymph nodes; 2. The lymphatic fluid of the upper part of the breast flows directly through the lymphatic vessels of the pectoralis major muscle into the subclavian lymph nodes, and then into the supraclavicular lymph nodes; 3. A part of the inner part of lymphatic fluid of the breast flows to the parietal lymph nodes (mainly in the second and third intercostal spaces, along the arterial and venous distribution of the thorax) through intercostal lymphatic vessels, and then to the supraclavicular lymph nodes; 4. lymph nodes (mainly in the second and third intercostal space, along the distribution of thoracic arteries and veins), and then drain to the supraclavicular lymph nodes; 4, through the subcutaneous lymphatic vessels between the breasts of both sides of the traffic, one side of the breast lymphatic fluid can flow to the opposite side; 5, the deep lymphatic network of the breasts may be connected with the rectus abdominis muscle sheath and the liver fusiform ligament of lymphatic vessels, which can make the deep lymphatic drainage of the breasts to the liver. The veins of the breast are accompanied by lymphatic vessels, which is of great significance in the hematogenous metastasis of breast cancer. The veins of the breast are divided into two groups: deep and superficial. The superficial group of veins is divided into two categories: transverse and longitudinal. The transverse vein passes through the pectoral muscle to the side of the sternum and converges into the internal mammary vein; the longitudinal vein travels to the supraclavicular fossa and injects into the superficial vein of the lower neck and then converges into the anterior jugular vein. The deep group of veins is divided into three routes: 1) injecting into the ipsilateral innominate vein through the perforating branch of internal mammary vein, which is an important route of hematogenous lung metastasis of breast cancer; 2) directly injecting into intercostal vein, and then introducing into the odd vein and superior vena cava through the traffic branch of intercostal vein and vertebral vein, which is the pathway of hematogenous metastasis of breast cancer to spine, pelvis and skull, etc.; 3) directly converging into the axillary vein, and then entering into the subclavian vein and innominate vein. 3. Directly converge into axillary vein, and then enter subclavian vein and innominate vein, which is another pathway of bloodstream lung metastasis of breast cancer.