The Breast Cancer Pathology Research Group is part of the multidisciplinary Nottingham Breast Cancer Research Group. We have a longstanding research interest and international track record in classification of breast cancer, diagnosis and development of breast disease, evaluation of prognostic and predictive factors in breast cancer and studying mechanisms governing hormone response in breast cancer. These include the Nottingham histological grading system, which has become the international gold standard for histological classification (WHO, UICC, EU and UK). The Nottingham Prognostic Index, also developed by the group, is regarded as the most effective system for clinical decision support in routine clinical management. Recently, it has been recognised that breast cancer develops as a consequence of a number of different specific molecular alterations, recognisable by molecular genetic and proteomic techniques, which manifest themselves as distinct and clinically relevant subgroups. We are now exploring the hypothesis that a novel classification of breast cancer based on phenotypic and molecular genetic characteristics will provide a more robust system for classification and therapeutic decision-making. As a consequence modern classification of breast cancer should be based on combined morphological, phenotypic (protein expression) and molecular genetic characteristics. This will provide a more robust system for classification and therapeutic decision-making and allow identification of novel therapeutic targets.