This study will examine two subsets of patients with breast cancer metastasis, that is, spreading, to the brain. It will identify genes and proteins that promote metastasis, particularly in women who are found to over-express (have more than other people do) the human epidermal growth factor receptor, ErbB2, also known as HER-2. The molecular and genetic events that permit tumor metastasis are not well understood. There is intense investigation going on into the process in which tumor cells escape the primary local tumor, spread to distant places in the body, and find and create conditions that promote growth in those tissues. Metastasis of tumors such as breast cancer to the brain is a common problem. Tumor cells will be analyzed with the use of microarrays. A microarray is a tool for analyzing gene expression, consisting of a small membrane or glass slide containing samples of many genes arranged in a regular pattern. The goal is to identify a potential molecular signature. It is hoped that there will be discovery of why some patients are more likely than others to develop a brain metastasis, which can have a major negative effect on the quality of life and survival.