Potential of Helicobacter pylori‐uninfected signet ring cell carcinoma to invade the submucosal layer

The typical histology of Helicobacter pylori-uninfected gastric cancer is signet ring cell carcinoma (SRCC) localized in the mucosal layer, but the potential of these SRCCs to invade the submucosal layer is unclear. This study aimed to investigate the clinicopathological characteristics of SRCC in H. pylori-uninfected patient and its prevalence in diffuse-type gastric cancer (DGC) within Japan.We enrolled consecutive pure DGC patients diagnosed with the disease either localized in the mucosal layer or with submucosal invasion. H. pylori infection was investigated, and the patients were divided into three groups according to histological types: pure SRCC, SRCC with poorly differentiated adenocarcinoma (PDA), and pure PDA.Of the 345 pure DGC patients, 132 (38%), 127 (37%), and 86 (25%) had pure SRCC, SRCC with PDA, and pure PDA histologies, respectively. The prevalence of H. pylori infection and the SM ratio were significantly lower in the pure SRCC group than other groups (P < 0.01). Twenty-two (6.4%) patients, including two with submucosal invasion, were negative for H. pylori and had mucosal SRCC component in the cancer lesions. Of the 259 SRCC cases (pure SRCC or SRCC + PDA), H. pylori-uninfected cases had different clinicopathological characteristics compared with H. pylori-positive cases. Particularly, the ratio of patients with submucosal invasive SRCC was significantly lower in the H. pylori-uninfected gastric cancer group than in those with H. pylori infection.Helicobacter pylori-uninfected gastric cancer is not rare among pure DGC patients in Japan. SRCC in patients without H. pylori infection is less likely to be invasive.