Updated: 9/15/2019

Islet Cell Tumors

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Snapshot
  • A 50-year-old woman presents to her primary care physician complaining of prolonged episodes of watery diarrhea, fatigue, and muscle weakness. Laboratory results demonstrate that she is hypokalemic with a normal anion gap metabolic acidosis. Fasting VIP plasma levels confirmed the diagnosis of a VIPoma (islet cell tumor) and octreotide was started for treatment.
Introduction
  • May involve any cell type in the endocrine pancreas
    • Zollinger-Ellison syndrome (gastrinoma) 
    • glucagonoma
    • insulinoma
    • somatostatinoma
    • VIPoma
    • non-functioning tumor
Glucagonoma
  • Neoplasm of α-islet cells
  • Presentation
    • symptoms
      • rash (necrolytic migratory erthema)
      • chelitis 
      • weight loss
      • diabetes mellitus
      • venous thrombosis
      • neuropsychiatric
    • physical exam
      • hyperglycemia
  • Treatment
    • surgery
    • medical
      • octreotide (somatostatin analogue)
Insulinoma
  • Neoplasm of β-islet cells
    • most common islet cell tumor
  • Association with MEN I
  • Presentation 
    • symptoms
      • mental status alterations
    • physical exam
      • hypoglycemia
  • Evaluation 
    • serology
      • ↑ insulin
      • ↑ C-peptide
        • important to distinguish patients who are injecting themselves with insulin (would be low)
  • Treatment
    • surgery
Somatostatinoma
  • Neoplasm of δ-islet cells
    • somatostatin is normally an inhibitor of most GI hormones
  • Presentation
    • symptoms
      • achlorhydria
        • blockage of gastin release
      • cholelithiasis
        • blockage of CCK release
      • steatorrhea
        • blockage of secretin release
      • diabetes mellitus
        • blockage of GIP release
  • Treatment
    • surgery
    • medical
      • combination chemotherapy
        • 5-fluorouracil
        • streptozotocin 
          • alkylating agent that targets cells arising from Islets of Langerhans
VIPoma
  • Neoplasm that produces ectopic vasoactive intestinal peptide (VIP)
    • normal functions of VIP
      • activates cAMP intestinal epithelial cells results in secretory diarrhea
      • vasodilation
      • inhbition of gastric acid secretion
      • stimulation of intestinal secretion
      • smooth muscle cell relaxation (lower esophageal sphincter)
  • Presentation 
    • symptoms
      • facial flushing
      • secretory diarrhea (also called pancreatic cholera)
      • achlorhydria
  • Evaluation
    • serology
      • hypokalemia
      • normal anion gap metabolic acidosis
      • resembles labs of other secretory diarrheas
      • hypercalcemia
  • Treatment 
    • surgery
    • medical
      • octreotide
Nonfunctioning tumors
  • Do not present with hormonal syndrome

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