Based on our observations and on the knowledge that other genes, such as PALB2, have been recently re‐classified from moderate to high‐penetrance BC susceptibility gene 45, we suggest that extreme caution is required in defining ATM‐ or CHEK2‐dependent cancer risk, and that at least extensive segregation analysis and LOH studies should be performed for each mutation, in order to more appropriately define the clinical utility of mutation detection for those genes. Here, CHEK2 is linked to breast cancer.