Dissecting the Heterogeneity of Breast Cancer*

Breast cancer is a highly heterogeneous disease with respect to its biology. In recent years, clinical and basic research have delivered data concerning tumor biology stemming from multiple methodological backgrounds,which in many cases are highly complementary to our understanding of breast cancer. For example, genetic profiling has identified subtypes of breast cancer that are both largely overlapping and complementary to data gathered in clinical research. In endocrine-related breast cancer, we can now not only formulate fairly good prediction,we can also link this knowledge to the molecular background of a tumor subtype. The following review attempts to summarize novel insights into breast cancer tumor biology as presented by representatives of clinical and basic research during the 2007 St. Gallen Consensus Meeting.