With the title of "Long-Term Outcomes of endoscopic-assisted vs conventional breast-conserving surgery in breast cancer patients after neoadjuvant therapy: a randomized, multicenter, open label, non-inferiority trial", this study targets breast cancer patients after neoadjuvant therapy. A total of 804 eligible patients, after screening with inclusion and exclusion criteria, will be randomly assigned to Endoscopic-assisted breast conserving surgery(E-BCS) or conventional breast conserving surgery (C-BCS) group at a 1:1 ratio using stratified block randomization method, stratified by centers and molecular subtype. The co-primary endpoints are 5-year disease-free survival (5y-DFS) and Breast-Q score at 6 months after surgery. The secondary endpoints are cosmetic outcomes including surgeons' satisfaction with breast and patients' satisfaction with scar, survival outcomes including 5-year overall survival (5y-OS) and 5-year local-recurrence rate (5y-LRR), surgical outcomes including operative time, intraoperative blood loss, incision length and postoperative complications rate. This study aims to confirm the long-term safety and aesthetic outcome of endoscopic-assisted surgery in breast cancer patients after neoadjuvant treatment by comparing it with conventional open breast conserving surgery, and provide clinical evidence for the popularized application of endoscopic breast surgery.