Abstract Background We report a case of an intraabdominal desmoid tumor that occurred at a gastro-pancreatic lesion with spontaneous cystic features, and present the successful laparoscopic resection of the tumor. Case presentation A 20-mm retroperitoneal cystic mass with a solid component was found adjacent to the stomach and pancreatic body in a 52-year-old woman with no history of familial adenomatous polyposis. Laparoscopic spleen-preserving distal pancreatectomy with wedge resection of the stomach was performed, and complete resection was achieved without intraoperative and postoperative complications. Histopathological examination by immunohistochemistry enabled diagnosis of a desmoid tumor that had originated from the stomach and invaded the pancreatic parenchyma with a spontaneous cystic change. We herein report an extremely rare case of an intraabdominal desmoid tumor with a spontaneous cystic change. Conclusion Regardless of its rarity, desmoid tumor should be included in the preoperative differential diagnosis of a cystic intraabdominal mass, and laparoscopic function-preserving surgery may be an optimal treatment option.
