This is a multicenter, retrospective observational study comparing the safety and efficacy of robotic-assisted versus endoscopic-assisted axillary lymph node dissection (ALND) in patients with node-positive breast cancer. The study aims to evaluate the protective effect on the intercostobrachial nerve (ICBN), perioperative outcomes, postoperative complications, and quality of life between the two minimally invasive techniques, as well as to assess long-term oncological outcomes including axillary recurrence and survival. Data will be extracted from routine clinical records. The study will compare the robotic group and the endoscopic group with respect to the following outcome measures:

1. ICBN-related sensory outcomes: incidence of sensory impairment (light touch, pinprick, cold, and warm sensations) in four key regions innervated by the ICBN (medial upper arm, axilla, lateral chest wall, and upper chest wall) assessed using standardized bedside sensory testing and sensory scoring systems;
2. Perioperative outcomes: including but not limited to operative time, estimated blood loss, number of lymph nodes dissected, length of hospital stay, drainage duration and axillary neurotomy;
3. Postoperative complications: including but not limited to seroma, hematoma, wound infection, lymphedema, and shoulder dysfunction;
4. Pain and functional outcomes: including but not limited to postoperative pain assessed by the Verbal Rating Scale (VRS), upper limb function assessed by the Disabilities of the Arm, Shoulder and Hand (DASH) score, and quality of life assessed by the Functional Assessment of Cancer Therapy - Breast + 4 (FACT B+4) questionnaire;
5. Oncological outcomes: including but not limited to axillary recurrence, locoregional recurrence, distant metastasis, disease-free survival (DFS), and overall survival (OS), with a minimum follow-up period to be determined based on data availability.

This study has been approved by the Research Ethics Committee of Guangzhou Medical University Affiliated Women and Children's Medical Center. A waiver of informed consent has been granted due to the retrospective nature of the study. All patient data will be anonymized and kept confidential. Statistical analyses will be performed using R, SPSS and GraphPad Prism, with a P value < 0.05 considered statistically significant.

Inclusion Criteria:

• pathologically confirmed breast cancer;
• clinical N1-N3 stage or confirmation of lymph node metastasis by intraoperative frozen pathology;
• Enlarged lymph nodes without significant adhesion to the axillary vessels or nerves;
• Ability to comprehend the research questions;
• Provision of informed consent and cooperation with the investigation;
• No history or current diagnosis of mental illness or impaired consciousness;
• ECOG PS 0-1.

Exclusion Criteria:

• Patients without lymph node metastasis;
• Patients who refuse surgery;
• Breast cancer patients with cognitive impairment, altered mental status, or inability to clearly express their feelings;
• Critically ill patients;
• Patients with other malignant tumors or severe medical conditions that render them unable to tolerate surgery.

Patients with breast cancer who underwent either robotic-assisted or endoscopic-assisted axillary lymph node dissection at the Department of Breast and Thyroid Surgery Center, Guangzhou Medical University Affiliated Women and Children's Medical Center and Foshan Fosun Chancheng Hospital.

Individual participant data will not be shared due to the retrospective nature of this study and concerns regarding patient privacy and confidentiality. The data were extracted from routine clinical records under a waiver of informed consent granted by the ethics committee, and the original consent forms did not include provisions for data sharing with external researchers. Therefore, IPD sharing is not planned. However, summarized data and analytical codes may be available from the corresponding author upon reasonable request, subject to institutional and ethical approval.