As a proof of principle, we compare small cohorts of breast tissue samples from women who underwent (i) reduction mammoplasty (RM) and (ii) prophylactic mastectomy (PM) due to an increased risk for hereditary breast cancer (BRCA1/2 mutations), as well as (iii) normal lobular tissue adjacent to neoplastic tissue (NT) from women with clinically manifest breast cancer. This evidence concerns the gene BRCA1 and breast cancer.