This result differs from that of a case–control study by Gronwald et al (2006) that included 285 BRCA mutation carriers with contralateral breast cancer and 751 matched controls, in which tamoxifen use was associated with a contralateral breast cancer risk reduction of 50% for BRCA1 carriers and 58% for BRCA2 carriers. The gene discussed is BRCA1; the disease is breast carcinoma.