Breast cancer is a multifactorial disease caused by a combination of environmental and genetic factors.1 In an estimated 10% of breast cancers, the genetic factor is contributed primarily by mutations in a single gene.2 Testing for BRCA1 and BRCA2 (BRCA1/2) has been available for more than two decades, and multiple professional organizations have developed guidelines for testing individuals based on suggestive personal or family history.3–7. Here, BRCA1 is linked to breast cancer.