 This study is a non-randomized Phase II study of the Axillary Reverse Mapping ARM procedure for patients presenting with breast cancer requiring lymph node evaluation. The study will enroll 100 subjects, and will have two study arms: one for patients requiring only the SLNB procedure roughly 67 of enrollees, and one for patients requiring a full ALND roughly 33 of enrollees. For the analysis of study efficacy, each arm will be compared to its procedure-appropriate historical control for evidence of decrease in the 1-year lymphedema rate among patients undergoing SLNB or ALND. 