Study Population: A series of women with breast cancer metastatic to the brain who do (n=39) or do not (n=39) over-express the growth factor receptor, HER-2, entered into a prospective trial in which pre-operative MRI imaging is performed as a matter of standard medical practice. At the time of this pre-operative MR, we propose to add one additional, 10-minute MR series, a dynamic, contrast-enhance image to assess the extent of blood flow through various aspects of the tumor.