Breast cancer is a common malignant tumor in clinical practice. The classification of breast cancer is generally divided into early, intermediate and late stages, but this simple classification does not have much substantive meaning and is not effective in guiding clinical treatment. At present, the more typical method used for breast cancer staging is the international TNM staging, where T refers to the primary focus, N refers to local lymph nodes, and M refers to the presence or absence of metastasis. Through TNM staging, breast cancer can be divided into four stages, stage I, stage II, stage III and stage IV. Stage I and stage II are relatively early cases of breast cancer, while stage III and stage IV belong to middle and late stage of breast cancer. This staging method has a very important significance in guiding the treatment of breast cancer. Surgery for early stage breast cancer can completely kill and cure breast cancer, and stage III and IV can be transformed into stage I and II by neoadjuvant chemotherapy or preoperative radiotherapy before surgery, which provides breast cancer patients a good chance for surgery. Therefore, the TNM staging currently adopted in clinical practice is of vital importance to guide and improve the cure rate and survival of breast cancer.