Small intestinal gastrointestinal stromal tumour with a coexisting retroperitoneal tumour: a case report and institutional review.

Gastrointestinal stromal tumours (GISTs) most commonly arise in the stomach or small intestine, whereas retroperitoneal lesions are rare. A 69-year-old woman without neurofibromatosis type 1 underwent single-incision laparoscopic resection for a high-risk jejunal GIST. Four months later, follow-up computed tomography revealed a 25-mm retroperitoneal tumour adjacent to the right common iliac artery, which had been retrospectively identifiable on the initial imaging. Laparoscopic excision was successfully performed, and pathological examination confirmed GIST. The patient resumed adjuvant imatinib therapy and remains disease-free at 12 months. Retrospective review of 18 surgically treated small intestinal GISTs at our institution showed that most multiple lesions were associated with neurofibromatosis type 1 or peritoneal dissemination, whereas the present case represented an exceptionally rare sporadic presentation. Careful imaging assessment and postoperative surveillance are essential for detecting atypical extra-gastrointestinal lesions.