ERBB2 and cancer: Given that hundreds of genes are causally implicated in the genetic alterations contributing to cancer, focus on individual genes as diagnostics, such as KRAS and HER2, provide limited gains in therapeutic efficacy; gene expression-fingerprints are similarly limited in their applicability, highlighting the urgent requirement for a robust, systematic approach to the identification and assessment of cancer biomarkers, which would be indicative of patient response to therapy.