Neuroendocrine neoplasms

Insulinoma (beta cell tumor)

Editor-in-Chief: Debra L. Zynger, M.D.
Diana Agostini-Vulaj, D.O.

Topic Completed: 24 April 2019

Minor changes: 26 October 2021

Copyright: 2002-2022,, Inc.

PubMed Search: Insulinoma[TI] pancreas[TI]

Diana Agostini-Vulaj, D.O.
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Cite this page: Agostini-Vulaj D. Insulinoma (beta cell tumor). website. Accessed January 21st, 2022.
Definition / general
  • Rare well differentiated neuroendocrine tumor of pancreas with functional production of insulin
Essential features
  • Tumor secretes insulin (analogous to beta cell production in normal pancreatic islets) and thus clinical hyperinsulinemic hypoglycemia is required for this diagnosis
  • Majority of insulinomas are small (< 2 cm) and benign
  • Multiple insulinomas associated with MEN1
  • Beta cell tumor
ICD coding
  • ICD-10: D37.8 - pancreatic neoplasm of uncertain behavior
  • Pancreas, more common in head
Clinical features
  • Whipple triad: symptoms of hypoglycemia (stupor, confusion, loss of consciousness), glucose < 50 mg/dL, symptoms relieved by glucose or symptoms caused by fasting or exercise
  • 10 - 15% associated with MEN1 syndrome; age < 20 years is suggestive of MEN1 (usually multiple tumors are seen) (Endocr J 2012;59:859, Best Pract Res Clin Gastroenterol 2005;19:783)
Radiology description
  • CT shows higher attenuation within the lesion than surrounding uninvolved pancreas in venous contrast enhancement phase
  • MRI allows better soft tissue contrast and identification of smaller lesions
  • On ultrasound, the lesion is characterized by low echogenicity and hypervascularity (Neuroendocrinology 2009;90:162)
Radiology images

Images hosted on other servers:

CT scan

Prognostic factors
Case reports
Gross description
  • More commonly solitary, well delineated lesion, with tan-yellow homogenous cut surface with or without hemorrhage (Surg Pathol Clin 2016;9:595)
Gross images

Images hosted on other servers:

Tail tumor

Well circumscribed mass

Microscopic (histologic) description
  • Trabecular, nested, gyriform or solid architecture
  • Monotonous cells demonstrating round nuclei with salt and pepper-like chromatin and abundant cytoplasm
  • Amyloid stromal deposition may be seen (Arch Pathol Lab Med 1978;102:227)
Microscopic (histologic) images

Contributed by Diana Agostini-Vulaj, D.O.

Well differentiated pancreatic neuroendocrine tumor, clinically an insulinoma based on laboratory findings

Positive stains
Negative stains
Electron microscopy description
  • Round secretory granules with paracrystalline content (similar to granules seen in B cells of normal pancreatic islets) (Nouv Presse Med 1977;6:3713)
Electron microscopy images

AFIP images

Left: crystalline granules; right: round haloed granules

Molecular / cytogenetics description
Sample pathology report
  • Pancreas, distal pancreatectomy:
    • Well differentiated neuroendocrine tumor, WHO grade__, functional, consistent clinically with insulinoma
Differential diagnosis
Board review style question #1
Which syndrome is associated with multiple insulinomas?

  1. MEN1
  2. MEN2A
  3. MEN2B
  4. NF2
  5. Peutz-Jeghers
Board review style answer #1

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Reference: Insulinoma
Board review style question #2
A midbody pancreatic enucleation is performed (see image below). Histologically, the neoplasm is positive for insulin, chromogranin and synaptophysin with a Ki67 of < 2%. The patient has no clinical syndrome of hyperinsulinemic hypoglycemia. What is the most appropriate diagnosis?

  1. Glucagonoma
  2. Insulinoma
  3. VIPoma
  4. Well differentiated neuroendocrine tumor, G1
  5. Well differentiated neuroendocrine tumor, G2
Board review style answer #2
D. Well differentiated neuroendocrine tumor, G1 (in the absence of a clinical syndrome, the term insulinoma should not be used; the Ki67 of < 2% classifies this as a grade 1 neuroendocrine tumor)

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Reference: Insulinoma
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