BRCA1 and ductal breast carcinoma in situ: But patients in studies above are almost from US and other Western countries, while only a few reports have been published concerning the prevalence of BRCA1/BRCA2 mutations with DCIS among Japanese people (Ikeda et al., 2001; Kawahara et al., 2004; Noguchi et al., 1999; Sekine et al., 2001).