Several hypotheses may explain this clinical phenomenon, including the poor or non-penetration of trastuzumab, a recombinant humanized anti-HER2 monoclonal antibody, across the blood-brain barrier, better imaging methods for the diagnosis of brain metastasis and the increased life expectancy of HER2-positive breast cancer patients with newer anti-HER2-targeted therapies [10]. The gene discussed is ERBB2; the disease is breast cancer.