Individuals carrying mutations in the CDH1 gene are at increased risk of developing stomach cancer (lifetime risk 7-42%) and breast cancer (lifetime risk 37-55%). Identification of these individuals through genetic testing is important because these cancers can be prevented by prophylactic surgery or detected early with endoscopy and breast imaging. Guidelines recommend genetic testing when certain clinical criteria are met. We previously showed that the widely used international criteria detected a small fraction of CDH1 mutation carriers, and we proposed simpler and more sensitive criteria, which were recently adopted by the National Comprehensive Caner Network (NCCN). Now, using a much larger dataset of 708 known CDH1 mutation carriers, we validate our previous findings, demonstrating that our criteria detect 82.2% of CDH1 mutation carriers, while the previously standard international criteria detect only 23.6%. (By Xavier Llor, MD, PhD, https://jmg.bmj.com/content/early/2024/12/13/jmg-2024-110446 )