It has been hypothesized that the proximity of the anatomic locations of the arm lymphatic drainage system to the breast lymphatic system in the axilla put the arm lymphatics at risk for disruption during a sentinel lymph node biopsy (SLNB) and/or axillary lymph node dissection (ALND). Therefore, mapping the drainage of the arm in addition to the drainage of the breast during the procedure would potentially decrease the incidence of arm lymphatic disruption and subsequent development of lymphedema while providing adequate axillary breast nodes needed for staging.