For instance, trastuzamab (Herceptin; Roche/Genentech, San Francisco, CA, USA), is used to treat breast cancer patients with HER2 (ERBB2) amplifications, imatinib (Gleevec; Novartis, Basil, Switzerland), is used to treat chronic myeloid leukemia only in patients that have a breakpoint cluster region, Abelson (BCR-ABL) fusion gene, and gefitinib (Iressa; AstraZeneca, Alderley Park, UK) works well in patients that have an activating mutation in the epidermal growth factor receptor (EGFR) receptor [3]. The gene discussed is ERBB2; the disease is breast cancer.