[Successful resection of a gastrointestinal stromal tumor in the pelvis with imatinib mesylate as neoadjuvant therapy].

We report a case of marginally resectable gastrointestinal stromal tumor (GIST) in the pelvis treated with neoadjuvant intent before subsequent successful surgical resection. A 46-year old man presented with urinary frequency and rectal discomfort with tenesmus. Computed tomography (CT) and magnetic resonance imaging (MRI) revealed a 12 cm diameter mass between the bladder and rectum and the margin of the tumor and prostate was unclear. No metastases were evident. Trans-rectal needle core biopsy confirmed c-kit positive GIST. Because of the locally advanced nature of the tumor,immediate surgical resection would have required total pelvic exenteration with eternal colostomy and urinary diversion. Therefore,the patient was treated with imatinib mesylate 400 mg daily in anticipation of adequate tumor size reduction to enable a more simplified surgical approach. After 3 months of imatinib therapy,MRI demonstrated a reduction in tumor size of 60%. Consequently,a complete surgical resection including the bladder,prostate and part of the sigmoid colon with temporary ileostomy and ileal conduit was performed. Pathological findings of the resected specimen showed widespread degeneration with cystic changes,necrosis, and hypocellularlity,as well as nodules of residual viable c-kit positive tumor cells. The patient has been treated with imatinib mesylate for 39 months following the operation without tumor recurrence.