A collection of both well-established and cutting-edge methods for investigating breast cancer biology not only in the laboratory, but also in clinical settings. These readily reproducible techniques solve a variety of problems, ranging from how to collect, store, and prepare human breast tumor samples for analysis, to analyzing cells in vivo and in vitro. Additional chapters address the technology of handling biopsies, new methods for analyzing genes and gene expression, markers of clinical outcome and progress, analysis of tumor-derived proteins and antigens, validating targets, and investigating the biology of newly discovered genes.