Abstract: Background and purpose: Whether axillary sentinel lymph node biopsy (ASLNB) could replace axillary lymph node dissection (ALND) in patients who converted after neoadjuvant chemotherapy (NAC) from cN+ to ycN₀ is still contentious, and the previous study only evaluated the pathological status of ALN without internal mammary lymph node (IMLN) condition. This study is to evaluate roles of ASLNB and internal mammary sentinel lymph node biopsy (IM-SLNB) in breast cancer patients after NAC. Methods: From Jan. 2012 to Dec. 2014, 60 breast cancer cT_1-4 N_0-3M₀ patients who were scheduled for neoadjuvant chemotherapy (NAC) and agreed to accept surgery after NAC from our department were enrolled into the retrospective study. Patients with cN₀ before NAC and ycN₀ after NAC underwent ASLNB (group A). Patients with cN₊ received NAC and ycN₀ after NAC (group B) were treated with ASLNB and ALND. Only patients whose clinical nodal status remained positive (ycN₊) after NAC underwent ALND without ASLNB (group C). All the patients received radiotracer injection and patients in group A and group B received blue dye injection additionally. Meanwhile, IM-SLNB would be performed for all patients with IMSLN visualization. Results: The number of patients enrolled in group A, group B and group C was 6, 45 and 9 cases respectively. The accuracy rate of ASLNB in group A was 100% (6/6). Only one patient was axillary sentinel lymph node (ASLN) positive performed ALND. With combination of blue dye and radiolabeled colloid, the accuracy rate of ASLNB in group B was 100% (48/48) and the false negative rate (FNR) was 17.9% (5/28). The FNR in patients with 1, 2 and >2 SLNs examined was 27.3% (3/11), 20.0% (2/10) and 0% (0/7). All of the ALNs were positive in group C. The visualization rate of IM-SLN was 63.3% (38/60). The detection rate of IM-SLNB was 97.4% (37/38) and the metastasis rate was 8.1% (3/37). The incidence of complications was 5.3% (2/38). Conclusion: ASLNB can be performed either before or after preoperative chemotherapy for patients with cN₀ disease. Among women with cN₊ converted to ycN₀ who had 3 or more SLNs examined, the FNR could return to be less than 10%. Those patients whose nodes are still ycN₊ should perform ALND. IM-SLNB should be performed routinely in all breast cancer patients after NAC, for it might help to make clear of the nodal staging and the pathological status of IM-SLN and provide the accurate indication of radiation to the internal mammary area in case of under-stage and under-/over-treatment, expecting to develop the definition of pathological complete response (pCR). 

Key words: Breast neoplasm, Neoadjuvant chemotherapy, Axillary sentinel lymph node biopsy, Internal mammary sentinel lymph node biopsy