Desmoid-Type Fibromatosis of the Proximal Jejunum Mimicking Gastric Gastrointestinal Stromal Tumor: Diagnostic Pitfalls in Determining the Tumor Origin

Abstract

ABSTRACT INTRODUCTION 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. CASE PRESENTATION 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. CONCLUSIONS 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.