Until now, the strongest evidence supporting ADCC as a key mechanism of some monoclonal antibodies was based on studies evaluating the impact of FcγRIIIa polymorphisms on clinical response to IgG1 mAbs such as rituximab in lymphoma patients (17, 18), trastuzumab in breast carcinomas (19) or cetuximab in colorectal carcinomas (6). The gene discussed is FCGR3A; the disease is breast carcinoma.