The current clinical staging is the TNM international staging method recommended by the International Union Against Cancer in 1959 and modified in 1978. The clinical staging of breast cancer is a determination of how far a breast cancer patient has progressed, which is of great significance in guiding treatment and determining prognosis. It depends on the following three aspects: 1) the growth of the cancer itself, including the size of the tumor and the extent of its infiltration, indicated by the word “T” (Tumor); 2) the extent of regional lymph node metastasis, indicated by “N” (Node); 3. The presence of hematogenous metastasis in distant organs, expressed as “M” (Metastasis). If 0, 1, 2 or 3 numbers are attached to the letters T, N and M to indicate the degree of change, the current clinical situation of a specific breast cancer can be clearly indicated. This is the clinical staging method adopted by the International Association Against Cancer, referred to as the TNM staging method. The histological manifestation of the tumor does not affect the classification of clinical staging. T represents the condition of the primary tumor. The T of most cancers can be classified into four grades, i.e. T1, T2, T3 and T4. The criteria for grading are firstly, the size of the mass and secondly, the local infiltrative manifestation. There are two other grades for certain carcinomas, namely T1S for carcinoma in situ T indicates no primary cancer foci were palpated. N represents the condition of regional lymph nodes. Clinically, it is also divided into four categories, i.e. N0, N1, N2 and N3. In order to indicate the presence or absence of lymph node metastasis in future pathological examination, “+” is added to N if metastasis is confirmed, and “-” is added to N if there is no metastasis. If there is metastasis in the lymph nodes that are not clinically palpable, it will be N0+, and if there is no metastasis in the palpable lymph nodes, it will be indicated by N1-. Clinicians can also append a or b to N to represent their judgment on the presence or absence of cancer metastasis in the lymph nodes they have palpated, e.g. N1a or N2a means the lymph nodes are palpable but considered non-cancerous metastasis, and N1b or N2b means the lymph nodes are palpable and considered to have cancer metastasis. M stands for hematogenous metastasis of distant tissues; M0 indicates no hematogenous metastasis of distant tissues, while M1 indicates metastasis of distant tissues. In this staging, Tis can only be clinically diagnosed if paget’s disease is limited to the nipple, while other carcinoma in situ cannot be clinically diagnosed, and N3 (metastasis of internal breast lymph nodes) is also not clinically palpable. Generally speaking, those with small cancer (less than 5 cm) and axillary lymph nodes cannot be touched are stage I; those with small cancer but enlarged axillary lymph nodes are stage II; and those with distant metastasis are all classified as stage IV regardless of the local growth of cancer or regional lymph node metastasis. Stage III is the most complicated, and T1N2 and T4N3 represent two extreme cases. Generally speaking, those with regional lymph node metastasis in the N3 range or local mass growth in the T4 range have a poor prognosis and can be considered for radiotherapy or chemotherapy before surgery to prolong life.