A rare case of Helicobacter pylori-uninfected intramucosal poorly differentiated adenocarcinoma that occurred in the gastric fornix

We report a rare case of undifferentiated-type intramucosal gastric cancer that occurred in the fornix of the stomach without Helicobacter pylori infection, which consisted mainly of poorly differentiated adenocarcinoma. A 49-year-old man visited our hospital for a follow-up endoscopic examination of a small depressed lesion of the gastric fornix detected by surveillance esophagogastroduodenoscopy. On magnifying endoscopy with blue laser imaging, the depressed lesion (approximately 10 mm in diameter) was regarded as undifferentiated-type early gastric cancer that proved to be a poorly differentiated adenocarcinoma by histological examination of biopsied specimens. The cancerous lesion was successfully treated with endoscopic submucosal dissection and microscopically showed an intramucosal cancer that invaded the whole mucosal layer with predominant growth of a poorly differentiated adenocarcinoma component. The patient status was verified as Helicobacter pylori-naïve according to the strict diagnostic criteria, thereby confirming this case as an undifferentiated-type Helicobacter pylori-uninfected gastric cancer. Helicobacter pylori-uninfected intramucosal poorly differentiated adenocarcinoma occurring in the gastric fornix has not been previously reported.