The CDH1 (E-cadherin, MIM *192090) gene is an ascertained and common cause of hereditary diffuse gastric cancer (OMIM #137215), an autosomal dominant condition with high penetrance (up to 76% at 80 years of age) for early-onset diffuse gastric cancer and lobular breast cancer [1]. This evidence concerns the gene CDH1 and Hereditary breast cancer.