Additional tyrosine kinase inhibitors (TKIs) targeting various cellular signaling pathways have entered the clinic since imatinib mesylate was approved by the FDA in 2001, including inhibitors targeting ERBB2 in breast cancer (Geyer et al., 2006) and the related RTK, EGFR, in lung adenocarcinomas (Ku et al., 2011). The gene discussed is ERBB2; the disease is breast cancer.