Somatostatinoma

  • Diagnosis
  • Background
  • Lab Tests
  • References
  • Related Topics

Indications for Testing

  • Neuroendocrine symptoms compatible with specific tumor; presence of pancreatic tumor with neuroendocrine symptoms

Laboratory Testing

  • Somatostatin level – usually elevated many-fold above normal
    • Intestinal somatostatinomas may have normal or only slightly increased levels
  • Provocative tests are available with infusion tolbutamide and arginine

Histology

  • Nested or trabecular arrangement of small- to medium-sized cells
    • Unique occurrence of psammoma bodies
    • Finely granular eosinophilic cytoplasm
    • Central round to oval nuclei
    • Stippled chromatin (“salt and pepper”)
    • Typically >5cm
  • Immunohistochemistry – synaptophysin, chromogranin A, Ki-67, NSE, PGP 9.5
    • Tumor-specific confirmation – somatostatin with diffuse immunoreactivity

Imaging Studies

  • CT/MRI/endoscopic ultrasound
  • Somatostatin-receptor scintigraphy

Differential Diagnosis

Somatostatinomas are rare, functional neuroendocrine tumors that produce excessive amounts of somatostatin. They occur in the pancreas and duodenum.

Epidemiology

  • Incidence – <1/1,000,000 (~10% of functioning PNETs)
  • Age – median is 40s
  • Sex – M<F, 1:2
  • Occurrence – usually sporadic

Risk Factors

  • Genetic
    • May also be associated with von Hippel-Lindau syndrome, tuberous sclerosis, and neurofibromatosis type 1 (von Recklinghausen disease)

Pathophysiology

  • Locations for tumor – duodenum (40%) or pancreas (60%)
  • 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; growth hormone)
    • Neurotransmitter function
  • Significant number of these tumors are metastatic

Clinical Presentation

  • Somatostatinoma syndrome
    • Diabetes mellitus – occurs in ~10% of intestinal and 75% of pancreatic tumors
    • Cholelithiasis – occurs in 60% of pancreatic and ~30% of intestinal tumors
    • 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
    • 80% of pancreatic and 50% of intestinal tumors are metastatic at presentation

Tests generally appear in the order most useful for common clinical situations. Click on number for test-specific information in the ARUP Laboratory Test Directory.

Somatostatin Quantitative, Plasma 2010001
Method: Quantitative Extraction/Immunoassay

Limitations

Modest somatostatin elevation may also occur in nonendocrine disorders

Follow Up

Modest somatostatin elevation may also occur in nonendocrine disorders

Synaptophysin by Immunohistochemistry 2004139
Method: Immunohistochemistry

Chromogranin A by Immunohistochemistry 2003830
Method: Immunohistochemistry

Pan Cytokeratin (AE1,3) by Immunohistochemistry 2003433
Method: Immunohistochemistry

Ki-67 with Interpretation by Immunohistochemistry 2007182
Method: Immunohistochemistry

Neuron Specific Enolase, Polyclonal (NSE P) by Immunohistochemistry 2004052
Method: Immunohistochemistry

Protein Gene Product (PGP) 9.5 by Immunohistochemistry 2004091
Method: Immunohistochemistry

Guidelines

NCCN Clinical Practice Guidelines in Oncology, Neuroendocrine Tumors. National Comprehensive Cancer Network. Fort Washington, PA [Accessed: Mar 2016]

O'Toole D, Grossman A, Gross D, Fave GDelle, Barkmanova J, O'Connor J, Pape U, Plöckinger U, Mallorca Consensus Conference participants, European Neuroendocrine Tumor Society. ENETS Consensus Guidelines for the Standards of Care in Neuroendocrine Tumors: biochemical markers. Neuroendocrinology. 2009; 90(2): 194-202. PubMed

Protocol for the Examination of Specimens from Patients with Carcinoma of the Endocrine Pancreas. Based on AJCC/UICC TNM, 7th ed. Protocol web posting date: June 2012. College of American Pathologists (CAP). Northfield, IL [Accessed: Nov 2015]

Protocol for the Examination of Specimens from Patients with Neuroendocrine Tumors (Carcinoid Tumors) of the Small Intestine and Ampulla. Based on AJCC/UICC TNM, 7th ed. Protocol web posting date: June 2012. College of American Pathologists (CAP). Northfield, IL [Accessed: Sep 2015]

Protocol for the Examination of Specimens from Patients with Neuroendocrine Tumors (Carcinoid Tumors) of the Stomach. Based on AJCC/UICC TNM, 7th ed. Protocol web posting date: February 2010. College of American Pathologists (CAP). Northfield, IL [Accessed: Nov 2015]

Vinik AI, Woltering EA, Warner RR P, Caplin M, O'Dorisio TM, Wiseman GA, Coppola D, Go VLiang W, North American Neuroendocrine Tumor Society (NANETS). NANETS consensus guidelines for the diagnosis of neuroendocrine tumor. Pancreas. 2010; 39(6): 713-34. PubMed

Öberg K, Knigge U, Kwekkeboom D, Perren A, ESMO Guidelines Working Group. Neuroendocrine gastro-entero-pancreatic tumors: ESMO Clinical Practice Guidelines for diagnosis, treatment and follow-up. Ann Oncol. 2012; 23 Suppl 7: vii124-30. PubMed

General References

Batcher E, Madaj P, Gianoukakis AG. Pancreatic neuroendocrine tumors. Endocr Res. 2011; 36(1): 35-43. PubMed

Garbrecht N, Anlauf M, Schmitt A, Henopp T, Sipos B, Raffel A, Eisenberger CF, Knoefel WT, Pavel M, Fottner C, Musholt TJ, Rinke A, Arnold R, Berndt U, Plöckinger U, Wiedenmann B, Moch H, Heitz PU, Komminoth P, Perren A, Klöppel G. Somatostatin-producing neuroendocrine tumors of the duodenum and pancreas: incidence, types, biological behavior, association with inherited syndromes, and functional activity. Endocr Relat Cancer. 2008; 15(1): 229-41. PubMed

Morgan KA, Adams DB. Solid tumors of the body and tail of the pancreas. Surg Clin North Am. 2010; 90(2): 287-307. PubMed

Oberg K. Pancreatic endocrine tumors. Semin Oncol. 2010; 37(6): 594-618. PubMed

Medical Reviewers

Last Update: January 2016