1337 Persistent Diarrhea in a Patient With a Pancreatic Tail Mass: VIPoma Diagnosed With Endoscopic Ultrasound-Guided Fine-Needle Biopsy

Abstract

INTRODUCTION: Vasoactive intestinal peptide-secreting tumors (VIPoma) are extremely rare with a worldwide incidence of 1 in 10 million per year. Approximately 56-80% of VIPomas metastasize before a diagnosis can be established. We present a case of a VIPoma localized to the pancreatic tail diagnosed with endoscopic ultrasound-guided fine needle biopsy (EUS-FNB) and treated successfully with octreotide and surgery. CASE DESCRIPTION/METHODS: A 64-year-old male presented with a 10-month history of gradually worsening diarrhea, muscle cramps, and a 30-lbs weight loss. He was tachycardic but hemodynamically stable. His abdomen was mildly distended and tympanic, but the remainder of his exam was unremarkable. Sodium was 125 mmol/L (ref: 135-146 mmol/L), potassium 1.6 mmol/L (ref: 3.5-5.1 mmol/L), bicarbonate 16 mmol/L (ref: 22-32 mmol/L), and chloride 87 mmol/L (ref: 98-107 mmol/L). Computed tomography showed a 4 cm lobulated, heterogeneously enhancing mass abutting the antero-inferior pancreatic tail with calcifications and pancreatic duct measuring 4.5 mm. Patient subsequently underwent EUS-FNB of the mass (Figure 1) with a 25-gauge fork-tip biopsy needle (Medtronic, Minneapolis, MN). Cytology revealed plasmacytoid cells with pleomorphic nuclei, abundant cytoplasm, and frequent naked nuclei indicative of neuroendocrine tumor (NET), grade II (Figure 2). Two consecutive vasoactive intestinal peptide (VIP) levels of 1170 pg/ml and 600 pg/ml (ref <75 pg/ml) along with an octreotide scintigraphy scan showing the presence of a radiotracer avid pancreatic tail mass, confirmed the diagnosis of VIPoma (Figure 3). Patient was started on octreotide and underwent laparoscopic distal pancreatectomy and splenectomy with resolution of symptoms. DISCUSSION: Pancreatic NETs are very rare and constitute only 1-2% of all pancreatic solid-mass tumors. VIPoma is one such NET and is intrapancreatic in 95% of cases. Approximately 56-80% of patients present with metastatic disease before a diagnosis is made. Also known as pancreatic cholera, VIPoma syndrome is characterized by a low osmotic gap secretory diarrhea, hypokalemia, hypochlorhydria, and acidosis. Infections, being more common, can delay diagnosis and treatment. Diagnosis is made by EUS-FNB and octreotide scan, as seen in our case. Treatment includes complete resection in rare cases where metastasis has not occurred. In patients presenting with secretory diarrhea and metabolic derangements in the setting of a pancreatic mass, EUS-FNB can be utilized to diagnose and stage the tumor.