BRCA1 and breast cancer: This is so because the germline inherited BRCA1/BRCA2 breast cancers are caused by only 1 or 2 hits and the spontaneous, sporadic breast cancers due to external radiation, hormone replacement therapy, dietary carcinogens, pesticides, etc. would be expected to bathe all the cells of the breast subjecting them to all of the “hits” required for carcinogenesis.