Five cases of gastric cancer in Helicobacter pylori-uninfected stomachs with Lynch syndrome.

Reports from Japan suggest that Helicobacter pylori infection could be a risk factor for gastric cancer in patients with Lynch syndrome (LS), similar to its role in sporadic gastric cancer. Therefore, eradication of H. pylori infection is recommended. However, the evidence regarding the risk of gastric cancer in H. pylori-uninfected patients with LS remains insufficient. Between 2014 and 2023, we encountered five cases of suspected LS-specific gastric cancer in H. pylori-uninfected patients during esophagogastroduodenoscopy (EGD) surveillance in individuals either genetically diagnosed with or suspected of having LS. This report describes the novel clinicopathological characteristics observed in these patients. A common endoscopic finding in all five cases was the presence of a characteristic elevated lesion with a reddish hue in the cardia or fornix. Histopathological examination confirmed LS-specific gastric cancer, including undifferentiated carcinoma. In cases initially presenting as subepithelial lesions, cancer diagnosis through biopsy was difficult. In tumors ≤ 15 mm, submucosal invasion is a key characteristic of H. pylori-uninfected gastric cancer with LS. This suggests the need for intensive endoscopic surveillance to detect rapid tumor growth.