Abstract
Desmoid-type fibromatosis (DTF) of the small intestine is rare and often mimics gastrointestinal stromal tumor (GIST). Its infiltrative growth can also make identification of the true organ of origin difficult. A 56-year-old woman was referred with a suspected gastric GIST based on imaging and endoscopic US-guided fine-needle aspiration. Before the planned surgery, the patient developed anorexia and vomiting. Emergency CT revealed rapid tumor enlargement with duodenal obstruction. Urgent multi-organ resection was performed, including partial gastrectomy, jejunal resection, partial pancreatic resection, and partial colectomy. Intraoperatively, the tumor appeared to originate from the stomach; however, histopathological examination revealed DTF arising from the jejunum with secondary invasion into adjacent organs. The postoperative course was complicated by an intra-abdominal abscess, which was successfully managed. No recurrence was observed 12 months after surgery. DTF should be considered in rapidly enlarging peri-gastrointestinal tumors with bowel obstruction. This case highlights the difficulty not only in differentiating DTF from GIST but also in accurately identifying the organ of origin.