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Pancreatic neuroendocrine tumor (PNET) is defined as islet cell tumors of the pancreas that make islet cell type hormones. PNET can be functional or non-functional.

Functional: (means the tumor made hormones cause symptoms and show elevation)

  • Insulinoma, Gastrinoma, Glucagnoma, VIPoma
  • Most functional are more benign but still difficult to predict behavior and require close follow up.

Non-functional: (hormones released do not cause symptoms or no elevation of hormone at all)

  • Does not see elevation of or hyperhormonal symptoms
  • Most non-functional are more malignant (determined based on metastasis) because difficult to predict behavior.

Cause and risk factors/Association:

  • MEN1 gene mutation has been associated with increased risk of endocrine tumors

Symptoms and Diagnosis of Pancreatic Neuroendocrine Tumors:

Non-functional:

  • Indigestion, diarrhea, epigastric/abdomen pain, jaundice, palpable mass at right upper quadrant that is usually non-tender.

Functional

  • Symptoms of excess hormones production depending on the type of hormones being excessively produced
  • Insulinoma:
    • Usually benign solitary (arise from beta cells), elevated insulin levels
    • Hypoglycemia especially post fasting and relieved with glucose in take
    • Whipple Triad (Low sugar, Hypoglycemia Symptoms, Reversal of Symptoms with Glucose)
  • Gastrinoma (ZES): see ZES section
    • Multiple ulcers (esophagus, stomach, duodenum, jejunum), elevated gastrin levels.
    • Can also arise from duodenum and peripancreatic tissues
    • Hypergastrenemia with ulcers refractory to conventional treatment.
    • Zollinger Ellison Syndrome (ZES): multiple duodenal ulcer, steatorrhea, prominent gastric rugal fold due to increase oxyntic gland mass
  • VIPoma
    • Tumors cells that produce excess VIP (vasoactive intestinal peptide)
    • Achlorhydria (low acid secretion from VIP);
    • Vasodilation (flushing, hypotension), nausea vomiting, weakness.
    • Hyperglycemia (due to increased glycogenolysis), hypercalcemia (due to increased bone resorption)
    • Watery Diarrhea with hypokalemia (hence muscle weakness), hypotension (due to loss volume).
    • Increased potassium secretion
    • Labs: stool studies show Osmolar gap < 50mOsm/kg, increased potassium ( Na+)
    • Diagnosis: VIP > 75 pg/ml confirms and watery diarrhea). CT abdomen (pancreatic lesion usually found on the tail of pancreas)

Lab Markers and Morphological features

  • See hormones for Functional PNET

Progression and Course of Disease

  • Hard to predict and need close monitoring.

Treatment and Management

  • Surgical resection for localized lesion (whipple procedure)
  • Some patient can choose the wait and watch approach if the lesion does not show aggressive behavior.
  • Chemotherapy if metastatic.