Genetic alterations in normal and malignant breast tissue

Breast cancer is a heterogeneous disease with a wide spectrum of morphological subtypes and a range of clinical behaviors. Over a long time period, pathologists have evolved a system of recording cancer-related data that reflects this heterogeneity as well as providing information relevant to prognosis and prediction of response to therapy. It is well established that subtype of breast cancer, grade, and stage (Ellis et al. 1992; Elston and Ellis 1991) provide prognostic information and the use of steroid receptor analysis as well as overexpression and amplification of HER2 provides prognostic and predictive data to manage patients (Oldenhuis et al. 2008). Nonetheless, there are limitations to these data and it is well known clinically that even within the same subtype (e.g., tubular carcinoma) or same stage of disease (e.g., lymph node positive), the behavior can be markedly different. Understanding the molecular abnormalities that drive the biology of each disease will assist our ability to specifically inhibit it. © 2011 Springer-Verlag London Limited.