Mutations in CDH1 cause the Hereditary Diffuse Gastric Cancer Syndrome. We report the largest series to date of index cases with a germline CDH1 mutation, and propose a revision of the testing criteria as a substantial proportion of our cases did not fulfil them. More specifically, we show that patients with a personal or family history of multiple breast cancers of the lobular type, even in the absence of diffuse gastric cancer, often carry CDH1 mutations. We also highlight the importance of identifying carriers early in order to offer them prophylactic gastrectomy before they develop highly-lethal, symptomatic diffuse gastric cancer. Finally, we propose for consideration the name “Hereditary Diffuse Gastric and Lobular Breast Cancer”, instead of “Hereditary Diffuse Gastric Cancer” to define the syndrome associated with germline CDH1 mutations.  (By Dr Patrick BENUSIGLIO, http://jmg.bmj.com/content/early/2013/05/24/jmedgenet-2012-101472 )