What happened, in summary

A 78-year-old Japanese man with a previous history of esophageal cancer surgery underwent regular stomach biopsies after atypical cells were first noticed in 2017. A later endoscopic examination found a 12-mm flat, elevated lesion in the body of the stomach. There was no visible evidence that the lesion had grown into the submucosal layer, so it was removed by endoscopic mucosal resection.

Pathology showed a rare gastric adenocarcinoma of the fundic gland type, predominantly resembling the chief cells normally found in fundic glands. The tumor was low grade and remained within the mucosal layer, with no lymphovascular invasion or surrounding desmoplastic reaction. Its staining pattern supported fundic-gland differentiation, and this rare tumor type is generally described as having low malignant potential.

A CT scan found no metastasis in the chest or abdomen. Endoscopy with repeat biopsy 2 months after the endoscopic resection found no remaining or recurrent neoplasm.