This shows that: 1. The lymph node metastasis of malignant tumor follows a certain pattern, that is, the tumor cells first drains to one or a few specific lymph nodes (SLN) in the region with lymphatic vessels, and then drains to other lymph nodes; 2. is very small, on the contrary, if SLN has metastasis, the possibility of metastasis in other lymph nodes in the region is greatly increased accordingly. Sentinel lymph node biopsy can avoid damaging the blood vessels, nerves and lymphatic vessels in the axilla, avoiding the occurrence of postoperative upper limb edema, dysfunction and abnormal skin sensation in the inner forearm, and the postoperative recovery is fast, which can shorten the hospital stay.