Discerning Clinical Responses in Breast Cancer Based On Molecular Signatures

Breast cancer represents a heterogeneous collection of diseases with disparate clinical behaviors, responses to treatment, and patient outcomes, despite common histopathological features at diagnosis. Examination of molecular signatures of breast cancer (based on complex gene expression patterns) enabled identification of several intrinsic molecular subtypes: luminal A, luminal B, human epidermal growth factor receptor 2 enriched, and basal like. The intrinsic subtypes are associated with measures of clinical aggressiveness, but do not perfectly predict patient outcomes. Several molecular signatures have been developed for prediction and prognostication of breast cancer outcomes. This review describes the molecular classification of breast cancer and the use of predictive/prognostic molecular signatures for guiding treatment decisions in breast cancer patients.