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Pancreatic Neuroendocrine Tumors (Islet Cell Tumors) Treatment (PDQ®): Treatment - Health Professional Information [NCI] - General Information About Pancreatic Neuroendocrine Tumors (Islet Cell Tumors)

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Diagnostic tests:

  1. BAO:MAO ≥ = 0.6 (Basal Acid Output:Maximal Acid Output).
  2. Overnight AO ≥ = 100 mmol.
  3. BAO ≥ = 10 mmol/hr.
  4. Serum gastrin 10 times normal or >500 pg/mL (the accuracy of gastrin assays may vary widely).
  5. Secretin test: 1 unit/kg IV rapid injection: Positive = 100% increase in gastrin within 10 minutes; 2 units/kg: Positive = 100% increase over baseline.
  6. Elevated human chorionic gonadotropin levels.

Insulinoma

Insulinomas are far more likely to be benign than malignant. Only 10% are multiple, and only 10% are malignant. About 5% to 8% are associated with MEN-1 syndrome.[4] The clinical manifestations are those of hypoglycemia, which results from inappropriate secretion of insulin by the tumor. Fasting hypoglycemia (<40 mg/dL) associated with an elevated insulin level (in the absence of exogenous administration of insulin) is pathognomonic. Measurement of plasma proinsulin may be helpful for diagnosing insulin-secreting carcinomas. These tumors are usually slow-growing tumors and, when localized to the pancreas or regional lymph nodes, can be cured with pancreatic resection.

The approach to management depends on carefully performed preoperative localization studies and the findings at exploratory laparotomy. In a retrospective case series of 30 patients with 32 pancreatic insulinomas, the combination of preoperative dual-phase thin-section multidetector CT and endoscopic sonography correctly identified and localized all of the tumors.[8] These tests, with or without MRI, have replaced older, more invasive, and technically challenging tests, such as percutaneous transhepatic portal venous sampling and arterial stimulation with venous sampling except for unusual circumstances in which the imaging tests are unsuccessful.[4,9]

Glucagonoma

Glucagonoma is the third most common endocrine-secreting islet cell tumor. About 75% of glucagonomas are malignant.[4] Necrolytic migratory erythema, hyperglycemia, and venous thrombosis comprise a virtually diagnostic triad. A serum glucagon level greater than 1000 pg/mL confirms the diagnosis. These tumors tend to be large and easily visible on CT scan. Somatostatin receptor scintigraphy scanning may be a useful adjunct in detecting metastases.

Miscellaneous Islet Cell Tumors

These tumors are rare but have defined clinical syndromes associated with specific production of polypeptide hormone production by islet cell tumors. Because of their rarity and similar approaches to management, they are grouped in the section on treatment. Miscellaneous tumors include the following:

  • VIPoma (Verner-Morrison Syndrome) is characterized by watery diarrhea, hypokalemia, and achlorhydria.

    A serum vasoactive intestinal peptide (VIP) greater than 200 pg/mL is diagnostic.[4] These tumors can generally be easily localized by CT scan. Somatostatin receptor scintigraphy scanning may be a useful adjunct in detecting metastases.

  • Somatostatinoma.

    These tumors are particularly rare. They often present with diarrhea, steatorrhea, diabetes, and/or gallstones. Decreased pancreatic secretion of enzymes and bicarbonate accounts for the diarrhea and steatorrhea. Somatostatin-mediated inhibition of cholecystokinin leads to gallstone formation. Somatostatin also inhibits insulin, producing hyperglycemia. The diagnosis is made by a fasting serum somatostatin level greater than 100 pg/mL. CT scan, MRI, and endoscopic ultrasound can usually help localize and stage the tumor. Most of these tumors are malignant and have metastases at diagnosis.

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