Poster Presentation ESA-SRB-ANZBMS 2024 in conjunction with ENSA

Hiding in plain sight: challenges of glucagonoma diagnosis in our metabolic syndrome epidemic (#621)

Emily Ludovici 1 , Joanna Gong 2 3 4 , Anushka Sharma 5 , Dhanushree Patel 5 , Emma Boehm 6 7
  1. Austin Health Clinical School, University of Melbourne, Melbourne, VIC, Australia
  2. Baker Heart and Diabetes Institute, Melbourne, VIC, Australia
  3. Department of Diabetes and Endocrinology, Royal Melbourne Hospital, Melbourne, VIC, Australia
  4. Department of Medicine, University of Melbourne, Melbourne , VIC, Australia
  5. Royal Melbourne Hospital, Melbourne, VIC, Australia
  6. Department of Cancer Imaging, University of Melbourne Centre for Cancer Research, Melbourne, VIC, Australia
  7. Department of Clinical Pathology, University of Melbourne Centre for Cancer Research, Melbourne, VIC, Australia

Glucagonoma, a pancreatic neuroendocrine tumour, is often diagnosed in later stages due to its rarity and non-specific symptoms. Early diagnosis is essential as pancreatic resection is the only curative treatment. Eighty percent of glucagonoma cases present with new-onset or worsening control of diabetes. Phenotypic similarities between hyperglycaemia resulting from glucagon excess and that associated with diabetes result in diagnostic delays.

We present this case of a middle-aged man with glucagonoma, on the background of long-standing type 2 diabetes mellitus.

This gentleman presented with deteriorating glycaemia, chronic diarrhoea, anaemia, depression, mouth ulcers and 4kg of unintentional weight loss over 6 months.

The focus of the patient’s work-up was for causes of diarrhoea. Colonoscopy and capsule endoscopy were unremarkable. Abdominal computer tomography (CT) scan incidentally detected a 20mm lesion on the pancreatic tail and an 8mm lesion on the uncinate process. 68Ga-DOTA-octreotate (GaTate) PET/CT scans revealed high somatostatin-receptor expression in both lesions, alongside further sub-centimetre DOTA-avid foci in the uncinate process, consistent with neuroendocrine tumours (NET). There was no evidence of loco-regional nodal or metastatic spread. The pancreatic tail tumour was classified on biopsy as a well-differentiated grade-1 NET (Ki-67=2%). Glucagon was 507 pg/mL (<140) and chromogranin A was 127 ng/L (<39). MEN1 genetic testing returned negative. After initial monthly subcutaneous lanreotide, a distal pancreatectomy and splenectomy was undertaken. The uncinate process NETs resolved with several rounds of radiofrequency ablation. The patient is now in remission, and under surveillance with 6-monthly PET scans.

This case report illustrates the challenges of diagnosing glucagonoma in patients with underlying diabetes or metabolic syndrome, particularly amid rising rates of these conditions. We seek to highlight gastrointestinal and constitutional “red flag” symptoms that should prompt investigation into rarer causes of hyperglycaemia, such as glucagonoma.