The purpose of this study is to map the arm lymphatic drainage system in the axilla with blue dye and the breast drainage system with a radioactive material. By identifying the arm lymphatics they can be protected during surgery and this may decrease the occurrence of lymphedema. The information obtained in this study may provide us with better surgical techniques to identify and protect the arm lymphatic drainage system in the axilla.

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.

Additional data will be collected on the treatment population's (a) variability in location of arm lymphatics, and (b) incidence of SLN crossover with arm lymphatics, along with success-rate data for identifying SLNs and arm lymphatics during SLNB and/or ALND. This additional data will add to our level of knowledge and experience regarding lymph node surgery.

Inclusion Criteria:

1. 19-100 years old
2. Not pregnant or breastfeeding
3. Breast cancer requiring LN evaluation for the breast
4. Willing participation following an informed consent process

Exclusion Criteria:

1. Patient < 19 y/o or > 100 y/o
2. Pregnant or breastfeeding
3. Allergy to blue dye
4. Locally advanced axillary disease
5. History of receiving neoadjuvant chemotherapy treatment
6. Prior axillary surgery or radiation therapy