Lapatinib is an oral, small molecule, dual tyrosine kinase inhibitor (TKI) that uniquely targets both the HER-2/ErbB2 and the epidermal growth factor receptor (HER-1/EGFR/ErbB1) (Oakman et al., 2010), making it a promising treatment option for trastuzumab-resistant patients with metastatic BC. The gene discussed is ERBB2; the disease is breast cancer.