Description

• Neoplasm of the pancreatic β cells of the islets of Langerhans leading to hyperinsulinemia. Pancreatic β cells manufacture proinsulin, which is then cleaved into insulin and C-peptide before secretion.
• Most common functional (insulin producing) tumor of the pancreas
• 90% are located within the pancreas.
• Usually small with 90% <2 cm; suspect malignant insulinoma if tumor is >4 cm.
• Symptoms due to hypoglycemia and concomitant cerebral glucose deprivation
• Diagnosis of insulinoma is often delayed due to vague and unusual presentation of neuroglycopenic symptoms.
• Hypoglycemic episodes are irregular, recurrent, and tend to increase in frequency and severity over time.
• Definitive management consists of surgical resection.
• Synonym(s): β-cell tumor; β-cell adenoma; nesidioblastoma

Epidemiology

Incidence

• 3 to 4 cases per 1 million person-years
• 10% malignant, 10% multiple tumors (1)
• Two major categories: sporadic (>90%) and multiple endocrine neoplasia type 1 (MEN1) syndrome (5–10%); etiology dictates treatment approach (2).
  • Sporadic type tends to be solitary and benign; sporadic type associated with slight female predominance (3)
  • When insulinoma associated with MEN1, usually accompanied by multiple lesions; patients typically present in the 3rd decade of life without significant gender-specific incidence (2).

Prevalence
The prevalence of insulinoma is 0.4% (4).
Genetics

• Mutations in DAXX and ATRX have been identified in 43% of pancreatic endocrine tumors (4).
• MEN syndrome associated with approximately 10% of cases; result of mutation in menin gene on long arm of chromosome 11 (2,5)

Risk Factors

MEN1 syndrome only known risk factor (1)

Commonly Associated Conditions

MEN1 syndrome (1)