P-43 Pancreatic insulinoma with delayed challenging diagnosis by 68Ga-DOTATATE PET/CT scan: Case report
Authors: Razzaq Khdair Hazbar , Al-Waeli Dheyaa , Abdulretha Mohanad , Mosa Hameed Naeem 
Published: January 2024

Introduction

Insulinoma (I) is most common neuroendocrine pancreatic tumor with an incidence of 0.1-0.3/100000(1). It is faintly more in females and can develop at any age(2). Usually benign, sporadic, less than 2 cm, solitary and in 10% of cases is multiple and happens as a component of multiple endocrine neoplasia syndrome type I (MEN–I)(3). Nonspecific symptoms may lead to delayed or misdiagnosis. Improper insulin secretion causes clinical features of hypoglycemia(2). Laboratory verification, localization followed by surgical removal are the main steps management. Localization may be difficult and delayed as here.

Clinical Case

A female of 58 years old with episodes of sweating, palpitation and tremor improved by drinking sweets, weight gain and denied any drugs intake. No personal or family history of diabetes or antidiabetic drugs. Body weight was 87 kg. Investigations during the attack showed low plasma glucose of 36 mg/dL, high serum insulin of 94.8 mIU/L (1.7 - 31), elevated C-peptide of 10.6 ng/mL (0.9-4).

Cortisol and thyroid function are normal. Abdominal ultrasound (US), CT scan and MRI are normal. Due to failure of localization of Insulinoma, treatment by diazoxide started with no response. Octreotide long-acting repeatable (Octreotide LAR) 20 mg monthly injection was initiated and increased to 30 mg monthly with good improvement and less attacks. After three years, the patient developed abdominal pain and abdominal US showed multiple gall stones. The patient was advised to do 68Ga-DOTATATE PET/CT Scan, which revealed distal pancreatic mass of 26 mm (Figure1A and B). Distal pancreatectomy and cholecystectomy had been done with smooth postoperative period normal normal plasma glucose, insulin and c-peptide with no further hypoglycemia, histopathological examination confirmed Insulinoma (Figure 2A and B).

Hypoglycemic symptoms of I, whether neuroglycopenic or sympathoadrenal are precipitated by fasting or exercise and could precede diagnosis by months and even years(3). Insulinoma, should be suggested when patient has typical Whipple's triad, high insulin, c-peptide and proinsulin during the attack(3). Weight gain noted in about 18% of cases(4).

Modalities used to localize Insulinoma include trans-abdominal US, CT scan, MRI, EUS (endoscopic ultrasound), intraoperative US, intraoperative palpation and arteriography. An American study considered 68Ga-DOTATATE PET/CT as an adjuvant tool for diagnosis with 90% detection rate (5). A 90-95% of cases are benign, patients have high survival with complete resolution of symptoms after excision with only 5.4% recurrences(6). Malignant I limited to pancreas and responsive to chemotherapy has 5 years survival rate after resection and 19 months for recurrent tumors(6).

Conclusion

Insulinoma should be considered in patients with typical clinical and laboratory finding. Follow up, assessment and different imaging techniques are main steps in management with teamwork.Figure 1.68Ga-DOTATATE PET/CT Scan68Ga-DOTATATE PET/CT Scan revealed distal pancreatic mass of 26 mm