Gastric adenocarcinoma of the fundic gland type: clinicopathological features of eight patients treated with endoscopic submucosal dissection

BACKGROUND: Gastric adenocarcinoma of the fundic gland type (GA-FG) has been added to the 2019 edition of the World Health Organization’s list of digestive system-associated cancers. This lesion differentiates toward the fundic gland and mostly involves chief cell-predominant differentiation with low-grade cytology. Clinicians and pathologists are still unaware of this rare disease; consequently, some cases are incorrectly diagnosed. This study aimed to investigate the clinicopathological features of GA-FG using retrospective analyses of endoscopic and pathological findings. MATERIALS AND METHODS: Samples were collected from patients diagnosed with GA-FG. The clinical courses of all patients were monitored prospectively and reviewed retrospectively. Available clinical information, endoscopic features, pathological appearance, and follow-up data were assessed. Immunohistochemistry [mucin (MUC) 2, MUC5, MUC6, P53, CDX2, Ki67, SYN, CD56, CGA, β-catenin, and pepsinogen-I] was examined using Envision two-step method. RESULTS: Eight cases of endoscopic submucosal dissection (ESD) were obtained from our institution. Patient age ranged from 48 to 80 years (mean, 65 years). Some patients were on acid-suppressing medication. Most lesions were located in the upper third (n = 7) and one was in the middle third of the stomach. Six lesions were of the superficial flat type, whereas two were of the superficial elevated type. Narrow-band imaging using magnifying endoscopy showed irregular microvascular patterns (MVPs) in four cases and regular MVPs in the remaining cases. All lesions were primarily solitary and ~ 6 mm in diameter (largest, 12 mm). The main body of the tumors were localized in the mucosal layer, of which six cases invade into the submucosal layer. Well-formed glands of chief cells were predominant. Tumor cells were positive for pepsinogen-I, MUC6, SYN, and CD56. Lymphatic and vascular infiltration and metastatic and recurrent disease were not observed in any case. CONCLUSION: GA-FG, a well-differentiated adenocarcinoma with mild atypia, can be completely removed using ESD, with a favorable prognosis in patients.