Trastuzumab is a humanised monoclonal antibody that binds to the domain IV of the extracellular segment of HER2 and has proven to be active in HER2-overexpressing breast tumours; the advantage of adding the monoclonal antibody to standard systemic treatments has been demonstrated in a meta analysis with consistent improvement in overall survival and progression-free survival (Harris et al, 2011). The gene discussed is ERBB2; the disease is breast neoplasm.