Signet ring cell carcinoma in situ, including pagetoid spread of signet ring cells, appears specific to HDGC with CDH1 mutations, as it has not been reported in SDGC (Carneiro et al., 2004; Fitzgerald et al., 2010) or HDGC without germline CDH1 mutations (van der Post et al., 2015b). The gene discussed is CDH1; the disease is Familial gastric cancer.