Molecular studies have definitely changed our knowledge of the biology of cancers, and breast cancer's tremendous social impact has stimulated a large mass of research. Classic markers have opened a road, but their usefulness appears limited to prognosis or follow up, while several new markers, both genetic and molecular, are assuming different, yet still controversial, importance: they may play a major role in the surveillance of subjects at risk, in detecting primary or recurrent cancers, and in predicting the need of adjuvant therapy, or the response to therapy. .