SUN-901 A Case of Coexisting Insulinoma and Islet Cell Hyperplasia

Introduction Insulinoma is the most common neuroendocrine tumour of the pancreas and cause of endogenous hyperinsulinemia hypoglycaemia. Islet cell hyperplasia is a rare cause of hypoglycaemia in adults. Clinical Case A 42-year-old lady presented with hyperphagia, giddiness, decreased concentration and weight gain of 10 kg over one year. Her symptoms occurred both during fasting and postprandial. She did not have any medical conditions and did not take alcohol. A 72-hour fast confirmed the presence of endogenous hyperinsulinemia; serum glucose of 2.4 mmol/L paired with insulin 8.14 mU/L and C -peptide 0.71 nmol/L occurring after 16 hours of fasting. Screening for sulphonylureas and meglitinides was negative. Serum beta-hydroxybutyrate was 0.1 mmol/L with a 1.6 mmol/L rise in serum glucose post 1 mg glucagon administration. Computed tomography (CT) of the abdomen showed a 13 X 11 X 15 mm exophytic lesion at the superior aspect of the pancreatic body and another exophytic projection measuring 9 X 8 X 6 mm arising from the tail. In view of possible multifocal insulinoma, a (68)Ga-DOTATATE scan was performed and it showed an intensely DOTATATE-avid exophytic nodule arising from the pancreatic body and a second indeterminate DOTATATE-avid nodule close to the pancreatic tail. In addition, there was diffuse DOTATATE uptake in the tail of pancreas. She underwent enucleation of pancreatic body nodule and spleen-saving distal pancreatectomy as the pancreatic tail nodule was not seen intra-operatively. Histology showed an insulinoma; a well-differentiated neuroendocrine tumour (Grade 1, pT1 N0 Mx) that was positively stained for synaptophysin, CD56, insulin, SSTR2 and SSTR5. The pancreatic tail nodule and distal pancreatectomy specimen showed islet cell hyperplasia; the pancreatic parenchyma showed multiple foci of well-circumscribed nests of bland islet cells with similar morphology to those seen in the insulinoma. She did not have further hypoglycaemia episodes post-operatively. Concomitant presence of fasting and postprandial hypoglycaemia may suggest underlying dual pathology. Clinical and biochemical differentiation between insulinoma and islet cell hyperplasia is difficult. Therefore, imaging for diagnosis and precise preoperative localisation is important for successful resection of suspected lesions. (68)Ga-DOTATATE scan can be as useful as (68)Ga-DOTANOC and (68)Ga-DOTATOC scan and is better than CT scan in localising not only insulinoma but also islet cell hyperplasia. In this case, islet cell hyperplasia-induced hyperinsulinemic hypoglycaemia may have persisted if distal pancreatectomy was not performed. Conclusion Adult-onset endogenous hyperinsulinemia hypoglycaemia can be caused by concurrent insulinoma and islet cell hyperplasia. (68)Ga-DOTATATE scan may be a useful, non-invasive investigation, especially in cases where CT imaging suggests multifocal disease.