The prevalence of BRCA1 and BRCA2 mutations among all women diagnosed with an invasive breast cancer or ductal carcinoma in situ is similar, and varies between 0.4–2.6% and 1.4–2.4%, respectively (Peto et al, 1999; Sanjose et al, 2003; Claus et al, 2005). The gene discussed is BRCA1; the disease is ductal breast carcinoma in situ.