A 77-year-old woman underwent an upper gastrointestinal (UGI) endoscopy screening examination, and a 10-mm reddish, submucosal tumor-like lesion was found on the posterior wall of the fornix. Biopsy was performed, but there was no evidence of malignancy, so annual follow-up by UGI endoscopy was decided upon. After 12 years, examination of another biopsy specimen revealed an adenocarcinoma of the fundic gland type. There had been no significant change in the size or shape of the lesion over the long follow-up period. Endoscopic submucosal dissection (ESD) was performed, and en bloc resection was achieved. Histopathologically, the tumor appeared as a flat elevated lesion measuring 11 × 10 mm. It was composed of irregularly shaped glands and invaded the submucosa up to 300 µm. Immunohistochemical examination involving specific antibodies to pepsinogen I, MIST-1, MUC6, and H+/K+-ATPase confirmed the fundic gland differentiation of the irregularly shaped glands together with a very low Ki-67 labeling index. Thus, gastric adenocarcinoma of the fundic gland type (GAFG) was diagnosed. Four years have passed since the ESD, and there has been no recurrence. To the best of our knowledge, this is the first report of the long-term natural history of GAFG. Over the 12 years, no morphologic changes were observed; the tumor remained within the submucosal layer. Our observations in this case strengthen the notion that GAFG is a specific type of gastric adenocarcinoma of low-grade malignancy.
Keywords: Endoscopic submucosal dissection (ESD); Gastric adenocarcinoma of fundic gland type (GAFG); Natural history.