Somatostatinoma

Somatostatinoma

 

Somatostatinomas are neuroendocrine tumors that produce excessive amounts of somatostatin and are located either in the duodenum or pancreas.

Epidemiology

  • Incidence – <1/million per year
  • Age – median age is 40-50 years
  • Sex – equal gender distribution
  • Occurrence – sporadic most of the time

Risk Factors

  • Genetic
    • Small percentage associated with multiple endocrine neoplasias (MEN 1)
    • Also may be associated with Von Recklinghausen disease (neurofibromatosis type 1)

Pathophysiology

  • Locations for tumor – duodenal or pancreatic
    • Presence of psammoma bodies in the duodenal tumor is suspicious for somatostatinoma
  • Hormone secretion is somatostatin
    • Inhibits the release of many hormones (gut hormones including insulin, pancreatic polypeptide, glucagon, gastrin, secretin, glucose-dependent insulinotropic peptide and motilin)
    • Neurotransmitter function
  • Significant number of these tumors are metastatic

Clinical Presentation

  • Somatostatinoma syndrome
    • Diabetes mellitus – occurs in about 10%
    • Cholelithiasis
    • Diarrhea/steatorrhea
  • Tumor may be found incidentally if not associated with the syndrome (patient will be asymptomatic)
  • Metastatic disease is frequently found at the time of diagnosis

Diagnosis

  • Laboratory testing
    • Somatostatin level – ≥160 pg/mL
  • Imaging studies
    • CT and/or MRI
  • Histological studies
    • Final confirmation of tumor type – special stains may be required

Differential Diagnosis

  • Diabetes mellitus (type 1 or 2)
  • Cholecystitis
  • Malabsorption syndromes
  • Other neuroendocrine tumors – VIPoma, carcinoid
  • Gastroenteritis

See Also