Islet cell tumours
Insulinoma: A usually benign isletcell tumour that may occur in the pancreas or at ectopic sites causing the hypersecretion of insulin. There may be gradual intellectual and motor impairment with insidious personality changes. Severe attacks of hypoglycaemia can produce sweating, palpitations, tremulousness and a range of bizarre psychoneurological behaviours. Patients may present with a hypoglycaemic coma. Histology shows encapsulated yellow/brown nodules containing cords and nests of well-differentiated β-cells.
Fasting hypoglycaemia with inappropriately high insulin secretion (exogenous insulin can be excluded by measuring C-peptide levels).
The tumour is found by conventional imaging in less than 50% of cases. Selective venous sampling of concentrations of insulin may be helpful, endoscopic ultrasound is increasingly being used.
Many pancreatic endocrine tumours express somatostatin receptors. Radiolabelled octreotide (a somatostatin analogue) can be used for localisation of the primary tumour and detection of any metastases.
Surgery is the treatment of choice.
Several options are available for the treatment of metastatic neuroendocrine tumors including octreotide, interferon α, chemotherapy and hepatic artery embolisation.
Glucagonoma: This is a very rare tumour of the islet cells of the pancreas which is often asymptomatic. Patients may present with necrolytic migratory erythema, painful glossitis, stomatitis, gastrointestinal upset, weight loss, diabetes mellitus and anaemia. Plasma glucagon levels are raised. Imaging and systemic treatment are as for insulinoma. Resection of the tumour is usually curative.
Other islet cell tumours: Very rarely islet-cell tumours secrete VIP or gastrin. VIPomas cause a profuse watery diarrhoea, hypokalaemia and achlorhydria. The patient may present as an acute abdomen, with ileus and abdominal distension suggestive of intestinal obstruction. Treatment is by resection where possible, or systemic treatment as for insulinoma. Gastrinomas cause the Zollinger–Ellison syndrome.