Molecular classification of breast carcinoma

Breast cancer is a complex disease encompassing multiple tumour entities each with a characteristic morphology and behaviour. Current clinical practice relies on the recognition of various pathology prognostic factors to guide patient management, including histological type and grade, stage and biomarker receptor status. However, there is increasing concern that these parameters are of limited value for the accurate prediction of individual patient outcome. The introduction of genome-wide microarray-based expression profiling studies has allowed better understanding of the molecular underpinning of several characteristics of breast cancer, including histological grade and metastatic potential. Expression profiling has also facilitated the identification of prognostic and predictive gene expression signatures and novel therapeutic targets. Here we review the evolution of molecular classification of breast cancer, including special types, the implications for clinical management, limitations of findings thus far and predictions for the future.