[A Case of a Duodenal GIST Observed as a Non-Functional Pancreatic Neuroendocrine Tumor].

A 67-year-oldman was referredto our hospital because his CEA level was increasing. In March 2007, abdominal computed tomography(CT)showedthe presence of a tumor(30mm in diameter)in the pancreatic head. Upon close inspection, the patient was diagnosed with a non-functional pancreatic neuroendocrine tumor and was observed. In September 2016, the patient showedhyperglycemia, liver dysfunction, andelevation of tumor markers. CT revealeda tumor(42mm in diameter) in the pancreatic head. It hadincreasedmore than before. We diagnosedhim with a gastrointestinal stromal tumor(GIST)of the duodenum based on endoscopic ultrasound-guided fine-needle aspiration biopsy and performed pancreaticoduodenectomy. Immunohistochemical staining showedpositive c-kit, andmore than 10%positive MIB-1. Currently, the patient is alive after the surgery.