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Key Features

Essentials of Diagnosis

  • GEP-NETs arise from the stomach, intestines, or endocrine pancreas

  • Secretory GEP-NETs present with different manifestations depending on the hormones secreted

  • Half of GEP-NETs are nonsecretory or secretory without clinical manifestations; they may be detected incidentally on scans or may present with weight loss, abdominal pain, or jaundice

  • Carcinoid tumors arise from the intestines or lung, secrete serotonin, and may metastasize

General Considerations

  • Pancreatic neuroendocrine tumors (pNETs) are of several types

    • A cells (20%) secrete glucagon

    • B cells (70%) secrete insulin

    • D cells (5%) secrete somatostatin or gastrin

    • F cells secrete pancreatic polypeptide

  • GEP-NETs

    • Once regarded as rare

    • Incidence has increased to about 37 per million yearly in the United States, due to the incidental detection of small tumors on abdominal scans

    • About 40% are functional, producing hormones that are tumor markers

  • Up to 25% of GEP-NETs are associated with one of four different inherited disorders

    • MEN-1

    • von Hippel-Lindau disease (VHL)

    • Neurofibromatosis 1 (NF-1)

    • Tuberous sclerosis complex (TSC)

  • Insulinomas secrete excessive amounts of insulin (as well as proinsulin and C-peptide)

    • Usually benign (90% of cases)

    • Solitary in 95% of sporadic cases, but multiple in about 90% of cases arising in multiple endocrine neoplasia type 1 (MEN 1)

  • Gastrinomas secrete excessive gastrin

    • About 50% are malignant and metastasize to liver

    • Typically found in duodenum (49%), pancreas (24%), or lymph nodes (11%)

    • Usually 5-year delay from symptom onset to diagnosis. Occur as part of MEN 1 in ~22%

  • Glucagonomas are usually malignant and usually co-secrete other hormones, eg, gastrin

  • Somatostatinomas and VIPomas (tumors secreting excessive somatostatin or vasoactive intestinal polypeptide) are very rare

  • CCKomas are rare tumors of the endocrine pancreas that secrete cholecystokinin

  • Carcinoid tumors

    • Can arise from the small bowel (53%, particularly terminal ileum), colon (12%), esophagus through duodenum (6%), or lung (bronchial carcinoid [5%])

    • Although usually indolent, metastases are common, particularly to liver, lymph nodes, and peritoneum

  • Nonfunctional pNETs

    • Produce no significant hormones

    • Usually grow to large size prior to detection

    • May secrete chromogranin A (CgA) or pancreatic polypeptide, which can be used as tumor markers

Clinical Findings

Symptoms and Signs

  • Nonfunctioning tumors typically present with mass effect and metastases, such as

    • Pancreatitis

    • Jaundice

    • Abdominal pain

    • Weight loss

  • Insulinoma

    • Secrete insulin

    • Fasting hypoglycemic symptoms

  • Gastrinoma

    • Abdominal pain (75%)

    • Heartburn (44%)

    • Bleeding (25%)

    • Weight loss (17%)

  • Glucagonoma

    • Weight loss, diarrhea, nausea, peptic ulcer, hypoaminoacidemia

    • Necrolytic migratory erythema

    • Diabetes mellitus develops in 35%

  • Somatostatinomas

    • Classic triad of symptoms

      • Diabetes mellitus because of its inhibition of insulin and glucagon secretion

      • Cholelithiasis because of its inhibition of gallbladder motility

      • Steatorrhea because of its inhibition of pancreatic exocrine function

    • Diarrhea, hypochlorhydria, and anemia

  • VIPoma (so called "WDHA" [or Verner-Morrison syndrome])

    • Watery Diarrhea (profuse)

    • Hypokalemia

    • Acidosis

  • CCKomas

    • May present with liver metastases and symptoms of diarrhea, peptic ulcer disease, and weight loss

    • Patients have elevated serum levels of ...

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