Abstract: Background and purpose: Sentinel lymph node biopsy has replaced axillary lymph node dissection as the standard staging procedure in early breast cancer patients with clinically negative axillary lymph nodes. It is a critical step for staging and treatment. This study investigated the localization effect of a novel tracer for breast cancer sentinel lymph node biopsy [indocyanine green (ICG)-rituximab (R)], using the hind limb drainage in mice as an animal model. Methods: For exploring the optimal dose and imaging time, different doses of ICG-R were injected subcutaneously to the dorsum of the foot in the BALB/c mice. Then the fluorescence vasculature imaging instrument was used continuously to observe the popliteal fossa lymph node (as sentinel lymph node) from the injection to 3 h after injection. For exploring the sustained localization effect, the optimal dose of ICG-R was injected and the imaging instrument was used from imaging to 24 h after injection. Results: The time from injection to imaging and the time from injection to the optimal imaging were shortened with the increased doses, and the imaging rate of the second or third level node increased accordingly. The best dosage of the novel tracer was 0.12 μg (dosage of indocyanine green) and the time from injection to the optimal imaging was about 34 min. After the observation for 24 h, the imaging rate of sentinel lymph node was maintained at 100%, and the imaging rate of the second and the third level lymph node increased from 0% to 20% and 10%, respectively. Conclusion: ICG-R could clearly locate the sentinel lymph node. There is no imaging of the second level lymph node within 6 h. The novel tracer has high value in the clinical application.

Key words: Breast cancer, A novel tracer for sentinel lymph node, Indocyanine green (ICG)-rituximab (R)