This prospective, single-arm, phase II trial studies axillary lymph node dissection (ALND) to see if it can be safely omitted in breast cancer patients with axillary pathological complete response (pCR) after neoadjuvant systemic therapy (NST). Breast cancer patients with biopsy-proven positive axillary lymph nodes at initial diagnosis, and converted to negative after NST, which is confirmed by Stained region Lymph Node Biopsy(SrLNB), will be enrolled in the study. In other words, a total of 92 patients will be exempted from ALND after SrLNB, and afterwards complete regional node irradiation (RNI) including the axilla. They will also undergo adjuvant chemotherapy, targeted therapy, endocrinotherapy after surgery. These patients will be followed up in the next three years for local-regional recurrence and long-time survival outcome.

Inclusion Criteria:

1. Female aged between 18 and 70 years;
2. Pathologically confirmed invasive breast cancer (regardless of pathological type) with a clinical stage cT1-3;
3. Pathologically confirmed positive axillary lymph nodes with a clinical stage of N1-3;
4. Receiving a full course of neoadjuvant therapy (including neoadjuvant chemotherapy, neoadjuvant targeted therapy, neoadjuvant immunotherapy);
5. Positive axillary lymph nodes successfully stained by carbon nanoparticles injection;
6. All patients are required to undergo immunohistochemical staining for Estrogen Receptor (ER), Progesterone Receptor (PR), human epidermal growth factor receptor 2 (HER2), Ki- 67 proliferation index, and further fluorescence in situ hybridization (FISH) should be performed in HER2 2+ cases;
7. Preoperative clinical assessment (including physical examination, imaging, with or without nomogram assessment) suggests positive axillary lymph nodes converted to negative (ycN0);
8. ECOG score 0 - 1;
9. Patients voluntarily participated in this study and signed the informed consent form

Exclusion Criteria:

1. Bilateral breast cancer;
2. Breast cancer during lactation period or pregnancy;
3. Physical examination or imaging examination confirmed presence of distant metastases;
4. Previous history of malignant tumor;
5. History of previous surgery on the affected axilla; or history of surgery affecting the function of the upper extremity;
6. History of radiation therapy to the breast or chest;
7. Positive incision margins for breast-conserving surgery/mastectomy;
8. Positive results of intraoperative rapid freeze pathology (including isolated tumor cells and micrometastases) for SrLNB (ypN+);
9. Those who unable to complete the full course of follow-up adjuvant therapy as prescribed for various reasons;
10. Aspartate transaminase (AST) and alanine transaminase (ALT) ≥ 1.5 times the upper limit of normal, alkaline phosphatase（ALP） ≥ 2.5 times the upper limit of normal, total bile ≥ 1.5 times the upper limit of normal, serum creatinine ≥ 1.5 times the upper limit of normal; Left Ventricular Ejection Fractions (LVEF) < 50% in cardiac ultrasound;
11. Severe coagulation dysfunction, serious systemic disease, or uncontrolled infection;
12. Without personal freedom and independent civil capacity;
13. Those with mental disorders, addictions, who were not eligible for enrollment in the judgment of the investigator.