S4761 A Rare Cause of Obscure GI Bleeding With Small Bowel Gastrointestinal Stromal Tumor

Introduction: Gastrointestinal Stromal Tumor (GIST) is an uncommon malignancy of the GI tract that arises from intestinal cells of Cajal. GIST can be found anywhere in the GI tract, but is most commonly found in the stomach, and can arise in the small intestine. GIST in the terminal ileum is a rare finding and presents as an indolent disease with severe complications due to a delay in diagnosis. This case illustrates an uncommon presentation of ileal GIST manifesting as overt lower GI bleeding and mimicking inflammatory or ulcerative etiologies. Case Description/Methods: A 58-year-old man presented to the hospital with symptoms of hematochezia, fatigue and blood loss anemia requiring frequent transfusions. During digital rectal exam, bloody stools were noted. He underwent an initial esophagogastroduodenoscopy (EGD) to rule out brisk upper GI bleeding, which was unremarkable; subsequently colonoscopy revealed a sessile tubular adenoma. He underwent a polypectomy; however, his lower GI bleeding persisted. At this point, a capsule endoscopy was done tha showed active bleeding from the terminal ileum prompting a retrograde deep enteroscopy that showed a large, ulcerated exophytic ulcer with bleeding which was treated with hemoclip and hemostatic spray. Initial biopsies were unremarkable with mixed inflammation without any malignancy. Subsequently, the patient underwent a surgical exploration that revealed a 3 cm exophytic tumor. Cecum and ileum were suspicious for creeping fat which is why a right colectomy with high ligation of ileocolic was done. Biopsies revealed spindle-to-epithelioid morphology, immunoreactive for DOG1 and c-kit, consistent with GIST. All margins were negative, and no peritoneal or hepatic metastases were observed. Discussion: This case highlights a unique presentation of GIST, as these tumors are not commonly located in the small intestine, with only a rare number of cases reported in terminal ileum. A study by Yang et al revealed small intestinal GISTs exhibited a significantly higher rate of gastrointestinal bleeding compared to gastric GISTs (P = 0.022). Additionally, it was noted that ileal GISTs had a higher prevalence of hematochezia (19.6%). Ileal GISTs have also been reported causing intussusception. These reports underscore the clinical variability and diagnostic challenges associated with ileal GISTs.