Insulinomas are the most common sporadic endocrine tumour of the pancreas.
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Account for 40% of syndromic pancreatic endocrine tumours. Overall incidence of ~0.0003%.
Typically insulinomas present with Whipple's triad consisting of:
- fasting hypoglycemia (<50 mg/dl)
- symptoms of hypoglycemia (due to subsequent catecholamine release)
- immediate relief of symptoms after the administration of IV glucose
As with other endocrine tumours of the pancreas, there is an association with multiple endocrine neoplasia type I (MEN I).
They develop from ductal pluripotent cells into unregulated cells secreting insulin. The beta cells of the islets of Langerhans normally secrete insulin. Approximately 10% of insulinomas are multiple and 10% malignant.
These tumours can be relatively small and multiphase contrast enhanced thin slice cross-sectional imaging is ideal. Most insulinomas are small (90% are <2 cm at presentation 3) and hypervascular. They may contain calcifications. Malignant tumours tend to be larger. Equally distributed between head, body, and tail of the pancreas.
They tend to be hyperattenuating on arterial phase so arterial or pancreatic phase imaging may aid in better detection 6-7. Some may show calcification.
Dynamic MRI with fast gradient echo sequences following bolus injection of contrast medium may aid the detection of these tumours 4:
- T1 C+ (Gd): typically shows enhancement, although contrast enhancement may not improve tumour visualisation compared with non-contrast images 4
Unlike other pancreatic endocrine tumors, insulinomas do not tend to express somatostatin analogs and somatostatin receptor scintigraphy is not generally useful for localisation.
- cystic neoplasm (cystic pancreatic mass differential diagnosis)
- solid neoplasm
- nonepithelial pancreatic neoplasms
- gallstone pancreatitis
- interstitial oedematous pancreatitis
- necrotising pancreatitis
- haemorrhagic pancreatitis
- revised Atlanta classification of acute pancreatitis
- chronic pancreatitis
- Ascaris-induced pancreatitis
- tropical pancreatitis
- autoimmune pancreatitis
- emphysematous pancreatitis
- hereditary pancreatitis
- pancreatitis associated with cystic fibrosis
- segmental pancreatitis
- acute pancreatitis
- pancreatic atrophy
- pancreatic lipomatosis
- pancreatic trauma
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- 5. Liessi G, Pasquali C, D'andrea AA et-al. MRI in insulinomas: preliminary findings. Eur J Radiol. 14 (1): 46-51. Eur J Radiol (link) - Pubmed citation
- 6. King AD, Ko GT, Yeung VT et-al. Dual phase spiral CT in the detection of small insulinomas of the pancreas. Br J Radiol. 1998;71 (841): 20-3. Br J Radiol (abstract) - Pubmed citation
- 7. Fidler JL, Fletcher JG, Reading CC et-al. Preoperative detection of pancreatic insulinomas on multiphasic helical CT. AJR Am J Roentgenol. 2003;181 (3): 775-80. AJR Am J Roentgenol (full text) - Pubmed citation