In Northern Europe familial clustering is seen in 10-20% of gastric cancer patients. In fewer than 3% a pathogenic variant in CDH1, the most important gene involved in hereditary gastric cancer, is detected. The majority of gastric cancer families remain genetically unexplained. We have sequenced a large cohort of unexplained familial gastric cancer patients for mutations in three recently described possible predisposition genes: CTNNA1, MAP3K6 and MYD88. Our data support that mutations in CTNNA1, but not MAP3K6, are a rare cause of gastric cancer susceptibility. No additional MYD88 mutations were detected suggesting that these are at most very rarely involved. (By Chella van der Post and Dr. Marjolijn Ligtenberg, http://jmg.bmj.com/content/early/2018/01/12/jmedgenet-2017-104962 )