Gene profiling in breast cancer.

Breast cancer is a heterogenous disease which shows a great variation in presentation and response to treatment. Currently, the most commonly used prognostic criteria are patient age, tumor size, lymph node status, tumor grade and hormone receptor status. These are however not very accurate. This is partly explained by the fact that they do not demonstrate the inherent genetic variability of breast cancer, which determines the aggressive nature and metastatic potential of the disease. Recent advances in molecular biology have demonstrated that breast cancer is not a single disease. The new diagnostic and prognostic tests based on molecular biology methods have helped identify molecular subtypes of breast cancer that are sensitive to chemotherapy and others that are resistant. This could provide valuable critical information and predict which patients would really benefit from chemo and/or hormonal therapy. Molecular biology will become increasingly important in clinical decision making and as the understanding of molecular processes within cancer cells grow, new targets for therapy will be discovered.