Somatostatinoma: Clinical manifestations, diagnosis, and management
- Emily Bergsland, MD
Emily Bergsland, MD
- Professor of Medicine
- University of California San Francisco
- Section Editors
- David M Nathan, MD
David M Nathan, MD
- Editor-in-Chief — Endocrinology
- Section Editor — Diabetes Mellitus
- Professor of Medicine
- Harvard Medical School
- David C Whitcomb, MD, PhD
David C Whitcomb, MD, PhD
- Section Editor — Pancreatic Diseases
- Professor of Medicine
- University of Pittsburgh School of Medicine
Somatostatinomas are rare neuroendocrine tumors of D-cell origin that contain and sometimes secrete excessive amounts of somatostatin (figure 1) . This topic will review the clinical manifestations, diagnosis, and management of somatostatinomas. An overview of the clinical manifestations, diagnosis, and management of pancreatic neuroendocrine tumors is discussed in detail separately. (See "Classification, epidemiology, clinical presentation, localization, and staging of pancreatic neuroendocrine tumors (islet-cell tumors)" and "Surgical resection of sporadic pancreatic neuroendocrine tumors" and "Metastatic well-differentiated pancreatic neuroendocrine tumors: Systemic therapy options to control tumor growth and symptoms of hormone hypersecretion" and "Metastatic gastroenteropancreatic neuroendocrine tumors: Local options to control tumor growth and symptoms of hormone hypersecretion" and "Insulinoma" and "Glucagonoma and the glucagonoma syndrome" and "Zollinger-Ellison syndrome (gastrinoma): Clinical manifestations and diagnosis" and "Management and prognosis of the Zollinger-Ellison syndrome (gastrinoma)" and "VIPoma: Clinical manifestations, diagnosis, and management".)
Somatostatinomas are rare neuroendocrine tumors with an annual incidence of 1 in 40 million . The mean age at diagnosis of somatostatinomas is 50 to 55 years (range 26 to 84), with a roughly equal gender distribution . Approximately 55 percent of somatostatinomas are in the pancreas, and, of these, two-thirds arise within the head of the pancreas. The remainder arises in the ampulla and periampullary region of the duodenum or rarely in the jejunum . Other rare primary sites include the liver, colon, and rectum [3,5]. Approximately 75 percent of somatostatinomas are malignant, and 70 to 92 percent present with metastatic disease .
Although 45 percent of somatostatinomas occur in association with multiple endocrine neoplasia (MEN)-1 syndrome, somatostatinomas are among the least common functioning pancreatic neuroendocrine tumors in patients with MEN-1 syndrome, occurring in less than 1 percent of patients . Up to 10 percent of patients with neurofibromatosis I (NF-1; von Recklinghausen disease) develop somatostatinomas. NF-1-associated somatostatinomas are characteristically duodenal, are rarely associated with somatostatinoma syndrome, and are less likely to metastasize as compared with sporadic somatostatinomas [4,8].
Somatostatin is a tetradecapeptide that normally acts in a paracrine manner to inhibit secretion of many hormones, including insulin, glucagon, gastrin, and growth hormone. It also has direct effects on a number of gastrointestinal functions . In patients with somatostatinomas, cholelithiasis may result from inhibition of cholecystokinin release, which reduces gallbladder contractility . Diarrhea and steatorrhea result from inhibition of pancreatic enzyme and bicarbonate secretion and intestinal absorption of lipids. Many patients with somatostatinomas also have gastric hypochlorhydria due to decreased gastrin secretion. (See 'Clinical manifestations' below and "Physiology of somatostatin and its analogues".)
Some somatostatinomas, particularly those arising in the ampullary and periampullary area, contain immunoreactive granules but are not associated with any functional syndrome [8,11]. In contrast, those arising in the pancreas may secrete large amounts of somatostatin, resulting in a constellation of symptoms of somatostatinoma syndrome. (See 'Clinical manifestations' below.)
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- CLINICAL MANIFESTATIONS
- TUMOR LOCALIZATION
- Approach to imaging
- DIFFERENTIAL DIAGNOSIS
- Pancreatic resection
- Treatment of advanced/metastatic disease
- - Somatostatin analogue
- - Liver-directed therapy for metastatic disease
- - Molecularly targeted therapy
- - Cytotoxic chemotherapy
- POST-TREATMENT SURVEILLANCE