Abstract Background: The axillary reverse mapping (ARM) procedure is based on the hypothesis that the lymphatic drainage from the upper arm is different from that of the breast. However, the oncologic safety of the procedure has not yet been determined. Methods: The ARM nodes were identified using a fluorescence imaging system. Sentinel lymph node (SLN) biopsy was performed in patients with clinically uninvolved nodes. If the SLN was positive, ALND was performed with removal of ARM nodes. Otherwise, the identified ARM nodes were preserved unless they were the same as the SLN. Results: The ARM node was identified in 30 of 91 patients who underwent SLN biopsy, and it was the same as the SLN in 23 patients. However, in 13 patients with a positive SLN who subsequently underwent ALND, ARM nodes were tumor-free when they were not the same as the positive SLN. Conclusions: There are limits to the principle of non-overlap between breast and arm nodes. However, it may be feasible to spare ARM nodes during ALND in patients with clinically negative nodes. Citation Information: Cancer Res 2011;71(24 Suppl):Abstract nr P3-07-44.