Endocrine Abstracts

Background: Insulinomas are rare pancreatic neuroendocrine tumours (pNETs), with over 99% arising within the pancreas. Ectopic insulinomas account for ~1% of cases and are diagnostically challenging due to atypical anatomical locations. Hepatic ectopic insulinomas are exceptionally uncommon, with only isolated cases reported.

Case Presentation: A 77-year-old woman presented with recurrent fasting-related hypoglycaemia, characterised by confusion, sweating, and loss of consciousness, all resolving with glucose (Whipple’s triad). A supervised 72-h fast confirmed endogenous hyperinsulinemia with markedly elevated insulin, C-peptide, and proinsulin levels and suppressed beta-hydroxybutyrate. Sulfonylurea screening was negative. CT and MRI revealed multiple bilobar hepatic lesions but no definite pancreatic mass. Ga-68 DOTATATE PET-CT demonstrated an intensely avid right mesenteric mass with multiple liver metastases and no further SSTR-positive disease. MRI pancreas showed chronic pancreatitis with coarse calcifications but no discrete tumour. Liver biopsy confirmed a well-differentiated Grade 2 neuroendocrine tumour (Ki-67 4%), positive for synaptophysin, chromogranin, and CD56. Diazoxide and dexamethasone were initially used for hypoglycaemia control but were discontinued due to hyponatraemia and progressive oedema. Octreotide was commenced, initially subcutaneously three times daily, then transitioned to Octreotide LAR 30 mg monthly. Following this, hypoglycaemic episodes completely resolved, with significant functional improvement and gradual weight regain. She remained independent with support and exhibited no symptoms of carcinoid syndrome. The HPB multidisciplinary team deemed the disease inoperable.

Discussion: Ectopic insulinomas most commonly arise from duodenal or gastric ectopic pancreatic tissue; hepatic origin is extremely rare. Advanced molecular imaging—including DOTATATE and GLP-1R–targeted Exendin PET—is invaluable in localising functional NETs when pancreatic imaging is inconclusive.

Conclusion: This case highlights the complexity of diagnosing ectopic insulinoma and the essential role of multimodal molecular imaging in guiding management.