Gene expression signatures in breast cancer distinguish phenotype characteristics, histologic subtypes, and tumor invasiveness.

Background: The development of reliable gene expression profiling technology is having an increasing impact on the understanding of breast cancer biology.

Methods: In this study, microarray analysis was performed to establish gene signatures for different breast cancer phenotypes, to determine differentially expressed gene sequences at different stages of the disease, and to identify sequences with biologic significance for tumor progression. Samples were taken from patients before their treatment.