Syndromes displaying a predisposition for breast cancer such as Li-Fraumeni syndrome (resulting from p53 gene mutations) [3], ataxia telangiectasia (ataxia telangiectasia-mutated, or ATM, gene) [4], and Cowden syndrome (phosphatase and tensin homologue, or PTEN, gene) [5] are estimated to account for no more than 10% of familial breast cancer collectively, and additional moderate-risk genes such as CHEK2 [6] and the recently reported BRIP1 (also called BACH1) [7] and PALB2 [8,9] account for an even smaller percentage. The gene discussed is CHEK2; the disease is breast cancer.