Abstract: Objective The aims of this study were to evaluate the risk factors of outer triangle tissue metastases,screen the patients with few outer triangle tissue metastases and discuss the significance of outer triangle tissue preservation. Methods A total of 150 patients underwent axillary lymph node dissection(ALND)in Harbin Medical University Cancer Hospital from September 2020 to June 2021 was conducted for this retrospective study.Patients were divided into two groups according to neoadjuvant therapy(NAC),with 95 patients in none NAC group and 55 patients in NAC group.The correlation between clinical data and outer triangle tissue metastases was analyzed.Multivariate logistic regression analysis was used to screen the risk factors and ROC curve was used to evaluate the combined diagnosis. Results In total sample,22 patients were detected outer triangle tissue metastases.Among 95 none NAC patients,19 patients(20%)had outer triangle tissue metastases.The size of lymph node in ultrasound was correlated with outer triangle tissue metastases(P=0.011).Multivariate logistic analysis showed that age ≤55 years,lymph node size and progesterone receptor condition were independent influencing factors for outer triangle tissue metastases.According to ROC analysis,the area under the curve was 0.820,specificity was 77.8%,sensitivity was 78.7%.Among 55 NAC patients,3 patients(5.5%)were detected outer triangle tissue metastases. Conclusion Lymph node size and pN stage are the influencing factors for outer triangle tissue metastases.Patients with NAC can be exempted from outer triangle tissue dissection.

Key words: Breast cancer, Outer triangle tissue, Axillary lymph node metastasis, Axillary lymph node dissection