{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,3,13]],"date-time":"2026-03-13T15:42:59Z","timestamp":1773416579090,"version":"3.50.1"},"reference-count":31,"publisher":"Frontiers Media SA","license":[{"start":{"date-parts":[[2025,7,7]],"date-time":"2025-07-07T00:00:00Z","timestamp":1751846400000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"content-domain":{"domain":["por-journal.com"],"crossmark-restriction":true},"short-container-title":["Pathol. Oncol. Res."],"abstract":"<jats:sec><jats:title>Background<\/jats:title><jats:p>Fundic gland tumors are a rare subtype of gastric tumors with fundic gland differentiation. This group of tumors has a low incidence rate and shows indistinctive cellular atypia, obvious structural atypia, special tissue morphology, and clinical prognosis, thus leading to diagnostic challenges.<\/jats:p><\/jats:sec><jats:sec><jats:title>Aim<\/jats:title><jats:p>We aimed to investigate the clinical and endoscopic characteristics and pathological features of gastric adenocarcinoma of the fundic gland (GA-FG) to provide a better understanding of this disease.<\/jats:p><\/jats:sec><jats:sec><jats:title>Methods<\/jats:title><jats:p>We collected data from patients diagnosed as having GA-FG at Guangdong Provincial People\u2019s Hospital between January 2019 and April 2024. The analysis focused on their clinical data, endoscopic characteristics, pathological morphological characteristics, immunohistochemistry results, treatment, and prognosis.<\/jats:p><\/jats:sec><jats:sec><jats:title>Results<\/jats:title><jats:p>Among the four patients were two men and two women (age range, 52\u201365\u00a0years). The tumors were mainly located in the gastric fundus and gastric body, and the lesions commonly had a superficial bulge. Three patients had an initial diagnosis of oxyntic gland adenoma, which was diagnosed as GA-FG after complete resection. These tumors were negative for MUC5AC, but showed diffuse strong positivity for MUC6 and pepsinogen I, and synaptophysin expression.<\/jats:p><\/jats:sec><jats:sec><jats:title>Conclusion<\/jats:title><jats:p>GA-FG is a rare gastric tumor with unique morphological features. As it is difficult to diagnose with a biopsy, immunohistochemistry plays an important role in the differential diagnosis. Oxyntic gland adenoma can be regarded as the intramucosal stage of GA-FG. Although all patients were negative for MUC5AC expression, MUC6 and pepsinogen I can help the diagnosis of GA-FG.<\/jats:p><\/jats:sec>","DOI":"10.3389\/pore.2025.1612163","type":"journal-article","created":{"date-parts":[[2025,7,7]],"date-time":"2025-07-07T05:10:20Z","timestamp":1751865020000},"update-policy":"https:\/\/doi.org\/10.3389\/crossmark-policy","source":"Crossref","is-referenced-by-count":1,"title":["Diagnostic challenges of rarely well-differentiated adenocarcinoma of the 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