Molecular diagnosis in breast cancer

Breast cancer is a complex and heterogeneous disease, encompassing a plethora of entities with distinct biological features and clinical behaviour. The advent of high throughput molecular methods has allowed a systematic characterization of the genomic landscape of breast cancer, revealing a profound heterogeneity in this disease. These methods are having a profound effect on the understanding of breast cancer. Some have already been incorporated in clinical practice, such as the prognostic ‘gene signatures’ that allow the tailoring of therapy in the subgroup of patients with oestrogen receptor (ER)-positive and HER2-negative breast cancer. In this review, we discuss the contribution of the main molecular methods in breast cancer research and how this information is changing our approaches to the diagnosis and management of this disease. We also address novel developments in the diagnosis and management of HER2-positive breast carcinomas and familial breast cancer.