Pancreatic Neuroendocrine Tumours
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Direct answer
Pancreatic neuroendocrine tumours are neoplasms of islet cells, and the functional types secrete hormones that produce recognisable syndromes. Insulinoma causes hypoglycaemia, gastrinoma causes Zollinger-Ellison syndrome, glucagonoma causes necrolytic migratory erythema, VIPoma causes watery diarrhoea with hypokalaemia, and somatostatinoma causes diabetes and steatorrhoea. Diagnosis rests on hormone measurement first, followed by localisation with imaging.
What you must remember
- Insulinoma: the commonest functional islet tumour, classically identified by the Whipple triad of hypoglycaemic symptoms, low plasma glucose during symptoms and relief after glucose.
- Insulinoma diagnosis: a supervised fast with raised insulin, C-peptide and proinsulin during hypoglycaemia, with a low C-peptide pointing to exogenous insulin and a sulfonylurea screen excluding drugs.
- Gastrinoma: Zollinger-Ellison syndrome, with peptic ulceration at unusual sites, diarrhoea and a raised fasting gastrin.
- Gastrinoma site: often in the duodenum, and the gastrinoma triangle of the duodenum, pancreatic head and neck guides localisation.
- Glucagonoma: necrolytic migratory erythema, diabetes, weight loss, anaemia and venous thrombosis, with raised fasting glucagon.
- VIPoma: the WDHA syndrome of watery diarrhoea, hypokalaemia and achlorhydria, with raised vasoactive intestinal peptide.
- Somatostatinoma: diabetes, gallstones, steatorrhoea and achlorhydria, from a tumour that secretes somatostatin.
- MEN1 link: gastrinoma and insulinoma are the commonest functional pancreatic tumours in multiple endocrine neoplasia type 1.
Hormone clues and the tests that confirm them
Each functional syndrome matches a specific hormone, and the syndrome often appears before localisation is complete. Biochemistry therefore comes first, followed by imaging to find the tumour.
| Tumour | Hormone | Syndrome and key test |
|---|---|---|
| Insulinoma | Insulin | Hypoglycaemia; supervised fast with raised insulin and C-peptide |
| Gastrinoma | Gastrin | Zollinger-Ellison syndrome; fasting gastrin with gastric acid hypersecretion |
| Glucagonoma | Glucagon | Necrolytic migratory erythema; raised fasting glucagon |
| VIPoma | Vasoactive intestinal peptide | WDHA syndrome; raised VIP level |
| Somatostatinoma | Somatostatin | Diabetes, gallstones, steatorrhoea; raised somatostatin |
Most functional tumours are small and need careful localisation, using CT or MRI, endoscopic ultrasound and somatostatin receptor imaging. Surgery is the definitive option where the tumour is resectable, while somatostatin analogues control hormone excess and symptoms when surgery is not possible.
Many pancreatic neuroendocrine tumours are non-functioning, so they present with mass effect, jaundice or an incidental imaging finding and need a different work-up. Hormone levels are then normal, and the decision rests on size, growth and imaging features rather than on syndrome.
Where the exam tries to catch you
Examiners test the diagnostic sequence for insulinoma and the recognition of diarrhoeal and rash syndromes.
- Trap: Diagnosing insulinoma from a single low glucose reading. Correct: The Whipple triad and a supervised fast with paired insulin and C-peptide confirm it, after exogenous insulin is excluded.
- Trap: Treating gastrinoma-driven peptic ulcers with antacids alone. Correct: Proton pump inhibitors control the acid load, and a raised fasting gastrin confirms Zollinger-Ellison syndrome.
- Trap: Calling VIPoma diarrhoea an infective problem. Correct: Watery diarrhoea with hypokalaemia and achlorhydria points to the WDHA syndrome and raised VIP.
Frequently asked questions
Which investigation confirms insulinoma?
A supervised fast with paired insulin, C-peptide and proinsulin measurements during hypoglycaemia confirms insulinoma. A sulfonylurea and meglitinide screen is needed first to exclude surreptitious drug use before localisation.
What is the Whipple triad?
The Whipple triad is hypoglycaemic symptoms, a low plasma glucose measured during those symptoms, and relief after glucose administration. It is the classic clinical criterion for insulinoma and directs the supervised fast that confirms the diagnosis.
Which syndrome is associated with necrolytic migratory erythema?
Glucagonoma is associated with necrolytic migratory erythema, diabetes, weight loss, anaemia and venous thrombosis. A raised fasting glucagon confirms the diagnosis, and the rash often appears before the tumour is found.
Which neuroendocrine tumours are most often part of MEN1?
Gastrinoma and insulinoma are the commonest functional pancreatic tumours in multiple endocrine neoplasia type 1, which also includes parathyroid and pituitary tumours. Screening for MEN1 is important when a functional tumour arises in a young patient or with a family history.