It is well known that sentinel lymph node biopsy has been available in the clinic for more than 20 years and has been widely used in breast cancer practice. The original concept was to assess the axillary situation of breast cancer patients through a less invasive sentinel lymph node biopsy (SLNB) to find evidence to reduce the extent of surgery and avoid axillary lymph node dissection. A series of studies have been performed to confirm that the use of axillary dissection in breast cancer patients with negative sentinel lymph nodes does not affect the disease-free and overall survival rates. One of the more representative studies is the Italian study. A prospective randomized controlled study with a single-center enrollment of 516 patients with 102 months of follow-up confirmed the safety of avoiding axillary dissection in SLNB-negative. Zhang Huiming, Department of General Surgery, Beijing Friendship Hospital, Beijing, China In 2006, sentinel lymph node biopsy has been included in the NCCN clinical practice guidelines for breast cancer; in 2009, the guidelines recommended that for breast cancer of I, II, when the local situation is suitable for lymph node biopsy, SLNB is the preferred method for axillary lymph node staging if an experienced SLNB team is available; in 2011, the Chinese edition of the NCCN guidelines, also recommended the The 2011 Chinese edition of the NCCN guidelines, also recommended the clinical application of SLNB. In the NCCN clinical guidelines for breast cancer, we can also see that SLNB is recommended for patients with stage I,II breast cancer with clinically negative axillary nodes who are suitable for SLNB, and that axillary lymph node dissection (ALND) can be excluded for patients with negative anterior lymph nodes (SLN), and this recommendation is obtained based on Class 1 evidence. On the other hand, we need to pay attention to the NCCN guidelines that recommend ALND for patients with positive SLNB or failure to biopsy SLN, but this is not a Class 1 evidence recommendation. The current national and international consensus considers positive SLN in breast cancer as an indication for ALND. However, based on clinical observations, it is found that in many patients with SLNB undergoing ALND, the proportion of non-sentinel lymph nodes with metastases is not high. Some patients with SLNB-positive non-ALND also do not have a high rate of axillary recurrence. Since SLNB technology originates from the concept of minimally invasive, how to allow more patients to achieve minimally invasive benefits through SLNB technology is a more important question for clinical researchers to focus on, whether SLN-positive patients need ALND and how to reduce unnecessary ALND are questions that need to be answered by researchers. The 2013 St. Gallen Expert Consensus: concluded that axillary clearance can be eliminated during surgical procedures if there are minimal metastases in the anterior sentinel lymph nodes, and that ALND can also be eliminated if there is breast-conserving surgery, the patient receives total breast irradiation postoperatively, and there are less than or equal to two positive metastases in the major anterior sentinel lymph nodes.These two consensuses are mainly based on the publication of the results of two studies. In the first study, the IBCSG 23-01 trial (International Breast Cancer Study Group 23-01 randomized trial), in this prospective study, 934 patients with tumors ≤5 cm and SLN with one or more micrometastases without extra-nodal invasion (<2 mm) were selected for enrollment and randomized into two groups with and without axillary clearance, and after a median follow-up of 5.0 years, it was found that the two groups of patients had There was no difference in disease-free survival between the two groups. In another study, the American College of Surgeons Oncology Group Z0011 randomized trial, a multicenter prospective controlled study, 856 patients with clinically negative axillary lymph nodes and 1-2 metastases in SLN were randomized into two groups: axillary cleared and non-cleared, and all patients received breast-conserving surgery plus radiotherapy and systemic adjuvant therapy. The ACOSOG Z0011 trial concluded that breast-conserving surgery with postoperative whole-breast irradiation and less than or equal to two intraoperative SLN metastases can safely avoid ALND. In the field of breast cancer treatment, the results of this study are considered to be practice-changing enough to change the norms of clinical practice. However, a careful analysis of the trial design and implementation of the ACOSOG Z0011 trial revealed certain problems with the study, including, on the one hand, the low enrollment of patients with invasive lobular carcinoma, the high number of hormone receptor-positive patients, the high number of HER-2 negative patients, the majority of patients >50 years of age, the majority of tumors <2 cm, and the absence of mastectomized patients, with less than 50% of the patients enrolled in the study. (It was estimated that 1900 patients needed to be enrolled, but due to the slow enrollment of cases (115 centers, less than 900 patients enrolled in 4 years), such enrollment constituted a lack of patients at high risk of recurrence; on the other hand, there were some shortcomings in the execution of the trial, as those with many axillary lymph nodes found intraoperatively needed to biopsy more than 3 SLNs to be enrolled, and there was no randomization, and there were more missing data from the trial. The number of SLN metastases was unknown in 98 patients (11%); tumor grade was unknown in 217 patients (32%); tumor size was unknown in 20 patients; and receptor status was unknown in 81 patients), and the percentage of missing follow-up was high (21% ALND group and 17% sentinel lymph node biopsy group missing follow-up). In addition, there is controversy regarding the treatment of patients enrolled in the group; standard whole breast irradiation may also subject the axilla (level I & II) to a non-negligible amount of radiation therapy, with the suspicion that radiation therapy replaces local control of axillary clearance therapy. There was a difference in tumor load of SLN tumor metastases between the two groups (62.5% of SLN bulk metastases in the ALND group and 55.2% in the SN group, and the local recurrence rate in the SN group was nearly twice that of the ALND group (0.9% V.S. 0.5%). Considering these factors mentioned above, breast surgeons should look critically at the findings of the study. Preserving the axilla in patients with breast cancer at high risk of recurrence eligible for the Z0011 trial should be done with caution; in patients with clinically negative axillae, positive T1-2, SLN1-2 envelopes, who undergo breast-conserving surgery and postoperative adjuvant whole-breast irradiation, axillary preservation may be selectively performed, whereas in mastectomized patients not receiving radiotherapy and in breast-conserving patients with partial breast irradiation and positive SLN, whether clearance of the axillae still needs further study.