Endosonography in Guiding Local Resection and Ampullary Preservation of a High-Risk Peri-Ampullary GIST - A Novel Approach

Abstract

Gastrointestinal stromal tumors (GIST) typically develop in the stomach or small intestine and rarely involve the ampulla of vater, with only 13 cases reported in the world literature. Most authors advocate performing pancreaticoduodenectomy (PD) for such lesions. We present a case of a high-risk, invasive peri-ampullary GIST and the multidisciplinary management approach to resection. A 61-year-old male presented to his primary care provider (PCP) for medication management. He had a history of chronic back pain and peptic ulcer disease (PUD). On routine laboratory testing, his Hgb was 8.8g/dL and endorsed 2 weeks of melena. Repeat Hgb was 9.2g/dL, Iron 17ug/dL, Ferritin 6ng/mL. Upper endoscopy revealed a 2.5cm submucosal lesion with a central ulceration (Fig 1). Standard forceps biopsy was obtained which revealed CD117 and DOG1 positive spindle cell subtype GIST but was insufficient for risk assessment. CT of abdomen and pelvis was read as a 2.6x1.4cm intraluminal mass involving the duodenum extending to the level of the ampulla. Endoscopic Ultrasound (EUS) was performed showing a hypoechoic round mass in the region of the major papilla arising from the muscularis propria layer to involve the mucosa and measuring 2.5cm by 1.6cm in maximum cross-sectional dimensions (Fig 2). Biliary and pancreatic ducts were of normal caliber and a core biopsy was obtained with a 22guage fine needle biopsy (FNB) needle (SharkCoreTM, Medtronic). Liver chemistry evaluation was normal. Core biopsy histopathology confirmed GIST but was unable to risk stratify by mitotic index. He subsequently underwent duodenal excision with complex reconstruction, pyloric exclusion, and Billroth II jejunostomy (Fig 3). Tumor capsule remained intact, a small portion of pancreatic head was resected due to tumor adherence. Final pathology showed a mixed-subtype, high-risk GIST involving duodenum and pancreas. His hospitalization was complicated by gastrojejunal anastomotic ulcer bleed and AKI. He recovered, and his renal function returned to normal. PD carries significant morbidity and mortality. Inconclusive risk-stratification of the GIST led to a multidisciplinary discussion regarding most effective yet least risky surgical approach to resection. Current literature suggests similar outcomes with local resection compared to PD for GIST's. Given the EUS findings of preserved ductal anatomy, our patient was referred and underwent successful local resection of the GIST with ampullary sparing.2552_A Figure 1. Endoscopic view of submucosal Gastrointestinal Stromal Tumor (GIST) and proximity to the ampulla of Vater.2552_B Figure 2. Endoscopic Ultrasound (EUS) with fine needle biopsy of GIST arising from the muscularis propria (MP).2552_C Figure 3. Intra-operative resection of GIST. Note proximity of tumor to the major papilla at the site of the biliary catheter.