A 66-year old man undergoing partial ileal resection for gastrointestinal stromal tumor (GIST) was diagnosed with multiple liver metastases seven months later. Imatinib mesylate administration was initiated, stabilizing tumors 1.5 years. After he reported abdominal pain, computed tomography (CT) showed an intestinally obstructive tumor. Laparotomy for suspected GIST recurrence radiologically showed an 8cm tumor in the ileal mesentery 210cm distal to the ligament of Treitz and 15cm proximal to the ileal anastomosis. After surgical resection, tumor cells were microscopically diagnosed as differentiated spindle fibroblasts with abundant collagen fibers but without karyomitosis. Immunohistochemically, cells were negative for c-kit, CD34, and S-100 but positive for β-catenin with nuclear translocalization, yielding a pathological diagnosis of mesenteric desmoid tumor. No desmoid tumors have been reported to develop during imatinib mesylate chemotherapy, and it was difficult to differentially diagnose these tumors preoperatively.
- Desmoid tumor
- Gastrointestinal stromal tumor
- Imatinib mesylate
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