S3212 An Occult Pancreatic Neuroendocrine Tumor Diagnosed by Endoscopic Ultrasound After Normal Imaging

Introduction: Functional pancreatic neuroendocrine tumors (PNETs) are a rare cause of chronic diarrhea, particularly vasoactive intestinal peptide-producing tumors (VIPomas). These tumors usually present with severe, symptomatic diarrhea and are often associated with widespread and aggressive metastases. However, the following case demonstrated a more indolent disease course, highlighting the variability in clinical presentation. Case Description/Methods: A 78-year-old man with a past medical history of hypertension and hyperlipidemia was referred for evaluation in the gastroenterology clinic for chronic diarrhea interfering with his quality of life. Two years prior, the patient had undergone a cholecystectomy, and his diarrhea was initially attributed to bile salt malabsorption. As part of the diagnostic process, bile salt binders were prescribed, but further evaluation for chronic diarrhea continued. By the time of his clinic visit, the patient’s symptoms had resolved. However, initial lab work revealed an elevated vasoactive intestinal peptide (VIP) level of 1200 pg/mL. Additional investigations showed no abnormalities, including a complete blood count, comprehensive metabolic panel, infectious stool studies, and abdominal Magnetic Resonance Imaging with intravenous contrast. Given the elevated VIP level, the patient underwent a PET DOTATATE scan, which revealed an area of kerning 3 at the pancreatic uncinate process concerning for PNET. Subsequently, endoscopic ultrasound (EUS) was performed, which identified a round hypoechoic mass measuring 7 × 5 mm in the head of the pancreas. Fine Needle Biopsy (FNB), which showed cells positive for CAM5.2 and synaptophysin, suspicious for PNET. The patient’s case was discussed at pancreas board, and options offered were surveillance, EUS-guided radiofrequency ablation, and surgery. Given his age and well controlled symptoms, he elected to pursue a surveillance strategy. Discussion: The case highlights the role of EUS in identifying small PNETs, which may not be identifiable on cross-sectional imaging studies such as computed tomography and magnetic resonance imaging. Surveillance, ablation, and surgery are all reasonable treatment options for well-differentiated PNETs less than 2 cm in size that are causing minimal symptoms. Our case demonstrates the importance of multidisciplinary management and individualized treatment decision making.