Abstract
BACKGROUND: Malignant transformation of an ectopic pancreas is exceptionally rare, posing significant diagnostic challenges. As such, there are currently no established management guidelines. We present a rare case of gastric adenocarcinoma arising from ectopic pancreatic tissue and provide a systematic review of previous case reports of adenocarcinomas derived from ectopic pancreas in the stomach, duodenum, and jejunum in the past 20 years. We provide an overview of the clinicopathological characteristics and discuss critical diagnostic and therapeutic considerations. CASE SUMMARY: A 58-year-old female was admitted to our hospital in August 2024 due to elevated carbohydrate antigen 19-9. Relevant examinations found a huge abdominal tumor that was radiologically adherent to both the pancreatic head and the greater curvature of the gastric antrum. A preoperative endoscopic biopsy-confirmed adenocarcinoma, prompting a pancreaticoduodenectomy. Histopathological examination subsequently identified the tumor as an adenocarcinoma originating from a gastric ectopic pancreas. Adjuvant chemotherapy (gemcitabine + capecitabine) commenced on November 13, 2024. After five cycles, surveillance imaging (April 3, 2025) revealed metastatic progression, prompting a transition to second-line therapy (nab-paclitaxel + gemcitabine). The patient is currently undergoing regular chemotherapy and has been followed up regularly, and the condition has not changed significantly compared with before. CONCLUSION: We hope that our findings will facilitate the clinical recognition of this entity and help to increase knowledge regarding its management.