Periampullary GIST Masquerading as a Pancreas Mass

Abstract

Introduction: Gastrointestinal stromal tumors (GISTs) rarely affect the periampullary region, with only a few anecdotal cases reported in the literature.Figure 1Figure 2Case Report: A 58 year old male with no significant past medical history had a CT of the abdomen performed at an outside hospital after sustaining a fall. In addition to a rib fracture, a 2 cm mass was visualized in the head of the pancreas. A follow up MRI confirmed a 1.8 cm enhancing lesion in the pancreaticoduodenal groove. The patient was referred for endoscopic ultrasound (EUS). Standard upper endoscopy was first performed revealing a subepithelial lesion in the second portion of the duodenum. During EUS, a round well-demarcated, 2 cm hypoechoic mass was visualized in the periampullary region. The pancreas parenchyma was normal throughout the pancreas. The common bile duct and pancreatic duct were normal in caliber and tapered normally to the ampulla. EUS guided fine needle biopsy was performed and histology demonstrated spindle cell proliferation and immunohistochemistry was positive for DOG-1, CD117, CD34, and SMA, consistent with a GIST. The patient is currently awaiting surgery for planned wedge resection. Conclusion: Duodenal GISTS are rare, accounting for 3-5% of GISTS and are especially uncommon in the periampullary region. Our case illustrates the importance of EUS with fine needle biopsy which determined the pancreas was not involved and also confirmed the diagnosis of GIST based on immunohistochemistry, allowing the patient to undergo a less invasive surgical option.