What is the characteristic of insulinomas (Insulinomas are tumors of the pancreas that produce excess insulin)?

Characteristics of Insulinomas

Insulinomas are mostly benign tumors, with approximately 90% being non-malignant, and they are typically solitary rather than multiple unless associated with MEN1 syndrome. 1, 2

Key Characteristics of Insulinomas

Benign vs. Malignant

• Approximately 90% of insulinomas are benign 1, 2, 3
• Only 5-10% of insulinomas are malignant 4
• 5-year survival rates are 94-100% for non-metastatic ("indolent") insulinomas 5

Solitary vs. Multiple

• Sporadic insulinomas (the majority of cases) are usually solitary 1, 2
• Multiple insulinomas typically occur in patients with Multiple Endocrine Neoplasia type 1 (MEN1) syndrome 1
• In MEN1 patients, insulinomas are often multiple and require different treatment strategies than sporadic cases 1

Relationship to MEN1 Syndrome

• Only 5-10% of insulinomas are associated with MEN1 syndrome 5
• Insulinoma and gastrinoma are the most common pancreatic neuroendocrine tumors in MEN1 patients 1
• Familial tumors (MEN1-associated) are typically multiple, whereas sporadic tumors are usually solitary 1

Anatomical Location

• Insulinomas can occur throughout the pancreas
• The surgical management varies based on location:
  • Exophytic or peripheral insulinomas are typically treated with enucleation 1
  • Tumors in the pancreatic head that are deep or invasive require pancreatoduodenectomy 1
  • Tumors in the distal pancreas are treated with distal pancreatectomy 1

Diagnostic Approach

• The gold standard diagnostic test is a 48-72 hour supervised fast 2
• Diagnostic criteria include blood glucose <55 mg/dL, insulin level >3.0 μU/mL, and C-peptide >0.6 ng/mL 2
• Localization is best achieved with endoscopic ultrasound (EUS), which can identify approximately 82% of pancreatic NETs 1, 2

Treatment Considerations

• Primary treatment for localized insulinomas is surgical resection 1, 3
• Preoperative management includes stabilizing glucose levels with diet and/or diazoxide 2
• Octreotide should be used with caution as it can worsen hypoglycemia in patients whose tumors are not somatostatin receptor-positive 2

Common Pitfalls

• Insulinomas may be small but still cause significant clinical symptoms due to hormone production 1
• Octreotide can paradoxically worsen hypoglycemia in insulinoma patients and should be used cautiously 2
• Insulinomas are less consistently octreotide-avid than other pancreatic NETs, which can affect imaging and treatment decisions 2

In summary, insulinomas are predominantly benign, solitary tumors that are only associated with MEN1 in a minority of cases. When associated with MEN1, they are more likely to be multiple. They can occur throughout the pancreas, with treatment approach varying based on location.