SUN-310 Duodenal Wall Insulinoma with Recurrence as Lymph Node Metastases

Abstract

Background: The overwhelming majority of insulinomas are intrapancreatic, but rare cases have been described outside the pancreas. The course of extrapancreatic insulinoma is unclear as there are no reported cases with follow-up beyond 3 months. We present a case of extrapancreatic insulinoma with recurrence as metastatic disease at 5-year follow-up. Clinical Case: In June 2013 a 36-year-old woman presented with Whipple’s triad and 40-pound weight gain. Her serum glucose was 49 mg/dL (normal range 70-99 mg/dL) with insulin level 8.1 uIU/mL (2.6 - 24.9 uIU/mL) and C-peptide 2.2 ng/mL (1.1 - 4.4 ng/mL) prior to receiving dextrose. 72-hour fast confirmed hyperinsulinemic hypoglycemia at 26 hours. Abdominal CT with IV contrast showed a 1.1 x 1.6 x 2 cm hypervascular mass in the second portion of the duodenum and a normal pancreas. OctreoScan did not show uptake in the area of the mass. Esophagogastroduodenoscopy found a mass in the duodenal sweep and endoscopic ultrasound (EUS) showed a 1.6 x 1.6 cm duodenal mass and 3 hypoechoic well-defined lymph nodes up to 1 cm in length distal to the mass. She underwent exploratory laparotomy with duodenotomy and neuroendocrine tumor (NET) enucleation in August 2013. Pathology showed a well-differentiated intermediate grade 1.5 cm NET with Ki-67 index 3-4%. 4/4 lymph nodes were negative for disease. After surgery, she had 30-pound weight loss and resolution of hypoglycemia at her 6-month follow-up. In September 2015 she had mild hypoglycemia (60-70 mg/dL) during exercise. 7-day continuous glucose monitoring (CGM) showed no glucose values <60 mg/dL, and abdominal CT with IV contrast did not show evidence of disease. Due to more frequent hypoglycemia symptoms, she had another 7-day CGM placed in July 2017 which showed 29% of glucose values <60 mg/dL and a pattern of hypoglycemia overnight. Abdominal CT was negative, but PET-CT with Ga68-DOTATATE showed a 1.5 x 1.3 cm soft tissue nodule adjacent to the inferior pancreatic head and wall of the 2nd portion of the duodenum with max SUV of 41. A 72-hour fast was not repeated. EUS showed normal duodenum and pancreas but found peripancreatic lymphadenopathy. Lymph node fine needle aspiration confirmed NET. Repeat surgery found metastatic well-differentiated NET to 5/12 lymph nodes with Ki-67 index 3.8%. Her hypoglycemia resolved after surgery. Follow-up Ga68-DOTATATE scan in January 2018 did not show evidence of disease. Conclusions: Extrapancreatic insulinoma is rare, and while few cases have been described there has not been long-term follow-up reported. This is the first known case of extrapancreatic insulinoma recurrence. Current evidence shows lymph node metastases of intrapancreatic insulinoma do not change prognosis (Krampitz, et al. Arch Surg 2012). It is unclear if this applies to extrapancreatic insulinoma. More long-term outcome data are needed to help determine how these patients should be monitored and managed.