DCIS and other premalignant lesions such as lobular neoplasia, fibroadenoma, and ductal hyperplasia seems to be more common in prophylactic mastectomy (PM) specimens of BRCA1 and BRCA2 mutation carriers than in control mammoplasty specimens [10], [39]–[42]. The gene discussed is BRCA1; the disease is ductal breast carcinoma in situ.