 Our goal is to investigate the use of 89Zr-trastuzumab as a HER2 imaging agent to determine which patients are likely to respond to targeted HER2 agents as single agent therapy. We are proposing to perform a pilot study with goals of demonstrating the feasibility of imaging breast cancer patients with 89Zr-trastuzumab-PETMRI, evaluating the relationship between tumor 89Zr-trastuzumab uptake and in vitro positivity of HER2, assessing the relationship between 89Zr-trastuzumab uptake and response to HER2 therapy. 