CDH1 and CDH1-related diffuse gastric and lobular breast cancer syndrome: In this way, despite our patient did not fulfill the strict criteria for HDGC, due to the young age of diagnosis, the histopathological analysis of the tumour (diffuse adenocarcinoma with signet-ring cells), and with an E-cadherin expression absent, she was tested for CDH1 mutations, and once she was found to have a pathogenic mutation, genetic testing was offered to some of her relatives.