Breast cancer is a clinically and genomically heterogeneous disease, and may therefore benefit from personalized therapeutic strategies. Incorporating genomic information obtained by molecular analysis of an individual patient’s tumor into treatment decisions is a promising area of focus. This approach requires knowledge of the genomic landscape and its possible therapeutic implications, but will ultimately allow employing investigational therapeutic compounds in a more intelligent way. Many institutes worldwide have contributed to the genomic landscaping of breast cancer, of which the results of six studies were recently published in Nature. These studies, summarized in Table 1, differ in breast cancer spectrum covered, primary focus, and technology platforms used. Integrating the genomic data from these studies, which is the focus of this review, provides an unprecedented opportunity to better understand the substantial variation in drug response and clinical outcome and to rethink treatment strategy.