Abstract: Objective To verify the secondary sentinel lymph node (SSLN) and for further exploration of refined sentinel lymph node biopsy (SLNB) for breast carcinoma via the assistance of preoperative contrast-enhanced ultrasound (CEUS) and novel crochet.Methods From December 2019 to November 2021,47 patients undergoing operation in the Breast and Thyroid Surgery Department of Peking University Shenzhen Hospital were prospectively collected.Preoperative contrast-enhanced ultrasound was performed for trace sentinel lymph node (SLN),SSLN and lymphatic channels.The SLNs were located by novel crochet.Meanwhile skin-marking was performed to label SLNs,SSLNs and lymphatic vessels.Intraoperatively,methylene blue and radioisotopes were adopted in SLNB.Both lymph nodes labeled preoperatively and intraoperatively were sent to the pathological department for definitive diagnosis,and the number of them was compared.Postoperative pathological features were analyzed.Results The CEUS identified a total of 62 SLNs in 47 patients,which are significantly fewer than methylene blue and radioisotopes(Z=-5.946,P＜0.05).The identification rate of positive SLNs was 11.29%,which is higher than methylene blue and radioisotopes(χ2=5.238，P＜0.05).A total of 83 SSLNs were identified by CEUS.The identification rate of SSLN and positive SSLN was 93.62% and 1.20% respectively.Conclusion The SSLN were successfully validated by preoperative contrast-enhanced ultrasound combined with crochet.

Key words: early-stage breast carcinoma, contrast-enhanced ultrasound, sentinel lymph node biopsy, secondary sentinel lymph node