Participants will:
* Receive a full course of standard neoadjuvant therapy for 6 or 8 cycles as clinically indicated
* Undergo preoperative screening assessments to confirm clinical axillary node negativity after neoadjuvant therapy
* Have 0.5ml of methylene blue injected into the areola before surgery and then receive personalized breast surgery combined with extensive sentinel lymph node biopsy plus axillary lymph node dissection
* Undergo pathological testing to count the total number of resected lymph nodes and metastatic lymph nodes in different axillary regions
* Receive adjuvant treatments like targeted therapy, endocrine therapy or local radiotherapy following clinical practice guidelines
* Attend clinic follow-up visits every 6 months for 2 years after surgery, including physical exams, surgical site checks and upper limb circumference measurements
* Allow their clinical, surgical, pathological and follow-up data to be collected and entered into a dedicated research database Report any physical discomfort or adverse events that occur during the study period to the research medical team in a timely manner
