Clinicopathological features of gastric adenocarcinoma of the fundic gland (chief cell predominant type) by retrospective and prospective analyses of endoscopic findings

<jats:sec><jats:title>Background and Aim</jats:title><jats:p>Gastric adenocarcinoma of the fundic gland type (chief cell predominant type) (GA‐FG‐CCP) is a variant of gastric adenocarcinoma with chief cell differentiation. GA‐FG‐CCP is rare and not well understood. The present study aimed to investigate the clinicopathological features of GA‐FG‐CCP using retrospective and prospective analyses of endoscopic findings.</jats:p></jats:sec><jats:sec><jats:title>Methods</jats:title><jats:p>A total of 20 patients including nine cases treated with endoscopic submucosal dissection (ESD) were diagnosed with GA‐FG‐CCP. Morphological changes were analyzed by retrospectively retracing past endoscopic records and following up after definitive diagnoses, including the status of <jats:italic>Helicobacter pylori</jats:italic> (<jats:italic>H. pylori</jats:italic>) infection.</jats:p></jats:sec><jats:sec><jats:title>Results</jats:title><jats:p>GA‐FG‐CCP were small and whitish lesions accompanied by atypical vascular growth and their macroscopic types were classified as 0‐IIa (60%), 0‐IIb (25%), and 0‐IIc (15%), respectively. The lesions were found in the non‐atrophic gastric mucosa of the upper (70%) or middle portion (30%), although gastric mucosal atrophy associated with current or past <jats:italic>H. pylori</jats:italic> infection was identified in 75% of cases. In the nine cases treated with ESD, submucosal invasion was identified in 80% of the resected lesions, but no lymphovenous infiltration was detected. Ki‐67 labeling index of GA‐FG‐CCP was low at 3.2% and visible morphological changes were rarely detected during long‐term endoscopic observation for 58.9 ± 13.1 months.</jats:p></jats:sec><jats:sec><jats:title>Conclusions</jats:title><jats:p>These data indicate that GA‐FG‐CCP, even when submucosal invasion occurs easily, might be of low‐grade malignancy as long as it is the chief cell predominant type without other epithelial abnormalities. In addition, GA‐FG‐CCP might develop despite <jats:italic>H. pylori</jats:italic> infection or gastric mucosal atrophy.</jats:p></jats:sec>