These genes include breast cancer susceptibility genes with high penetrance (CDH1, NBS1, NF1, PTEN, TP53, and STK11), moderate penetrance (ATM, BRIP1, CHEK2, PALB2, and RAD50), and low penetrance (FGFR2, LSP1, MAP3K1, TGFB1, and TOX3).1 The United States and most countries in Europe have professional genetic services programs that provide genetic testing and counseling regarding the risk of developing breast cancer. The gene discussed is CDH1; the disease is breast cancer.