[A Case of Mesenteric Desmoid Tumor Arising during Follow-Up of the Clinical Course of Ulcerative Colitis]

A man in his 50s with a known history of ulcerative colitis under regular surveillance in our gastroenterology department. He presented with right lower quadrant abdominal pain and a sense of abdominal distension. Contrast-enhanced CT revealed a well-circumscribed, mildly enhancing intra-abdominal mass measuring 12×8×13 cm. MRI showed a heterogeneously hyperintense lesion. Differential diagnoses included gastrointestinal stromal tumor(GIST)and other mesenteric tumors. For definitive diagnosis and treatment, an open surgical resection was performed. The tumor originated from the mesentery of the terminal ileum and was adherent to the descending portion of the duodenum. Ileocecal resection and wedge resection of the duodenum were performed, and the tumor was excised. Histopathological examination confirmed the diagnosis of an intra-abdominal desmoid tumor arising from the mesentery.