The purpose of this study is to identify tumor cells in the bloodstream (Circulating Tumor Cells, CTC's) from patient's with locally advanced or metastatic (stage IV) breast cancer. Analyzing the tumor is helpful in guiding therapy; however, research has suggested that the number of tumor cells found in the bloodstream (CTC's) signifies more aggressive behavior and increased difficulty in eliminating the cancer. This research will help to develop better ways to treat breast cancer which could be tailored to a patient and may be adjusted to a patient's individual needs.