Abstract:ObjectiveTo investigate the application of ^99mTc-sulfur colloid (^99mTc-SC) lymph node imaging with methylene blue tracing during sentinel lymph node biopsy (SLNB) procedures and its importance in evaluating axillary lymph node metastasis and safety. Methods A total of 121 breast cancer patients admitted to Zhuhai Hospital of Integrated Traditional Chinese and Western Medicine from December 2017 to December 2022 were selected,and were randomly divided into the methylene blue group（n=41）, the ^99mTc-SC group （n=40）and combination group（n=40）. All patients recevied SLNB under the tracing of methylene blue, ^99mTc-SC radionuclide imaging, or the combination of the two ,and followed by axillary lymph node dissection. Based on the pathological results after SLNB, the diagnostic efficiency of three methods for sentinel lymph nodes was analyzed.Results There was no significant difference in the detection accuracy, specificity, sensitivity and false negative rate of axillary sentinel lymph nodes among the three groups (P>0.05).The detected number of axillary positive lymph nodes in methylene blue group (2.79±0.98), ^99mTc-SC group (3.25±1.25), and combination group (3.97±1.06) increased sequentially (F=11.78, P<0.01), and the differences of pairwise comparisons were also statistically significant (P<0.05). Urine blue staining occurred in 4 cases of methylene blue group and 1 case of combined group, and the urine color of all patients returned to normal within 24 hours, and〖JP〗 〖LM〗no other adverse reaction was observed. Conclusion The combination of ^99mTc-SC and methylene blue as a tracer can improve the detected number of axillary positive lymph nodes, which has high application value in SLNB of breast cancer.