Differential Diagnosis for Elevated Blood Levels of NETs

• Single most likely diagnosis:
  • Carcinoid syndrome: This condition is characterized by the excessive production of serotonin and other vasoactive substances by neuroendocrine tumors (NETs), leading to elevated blood levels of these substances. The symptoms include flushing, diarrhea, wheezing, and heart valve abnormalities.
• Other Likely diagnoses:
  • Neuroendocrine tumors (NETs) without carcinoid syndrome: These tumors can produce various peptides and hormones, leading to elevated blood levels of these substances. The clinical presentation varies depending on the type and location of the tumor.
  • Medullary thyroid carcinoma: This type of thyroid cancer can produce calcitonin, a hormone that can be elevated in the blood. It is often associated with multiple endocrine neoplasia type 2 (MEN2).
• Do Not Miss diagnoses:
  • Pheochromocytoma: Although less common, this tumor of the adrenal gland can produce catecholamines, leading to life-threatening hypertension and other symptoms if not promptly diagnosed and treated.
  • Insulinoma: A tumor of the pancreas that produces excess insulin, leading to hypoglycemia, which can be life-threatening if not recognized and managed properly.
• Rare diagnoses:
  • VIPoma: A rare pancreatic tumor that produces vasoactive intestinal peptide (VIP), leading to severe diarrhea, hypokalemia, and achlorhydria.
  • Glucagonoma: A rare tumor of the pancreas that produces excess glucagon, leading to hyperglycemia, skin rash, and weight loss.
  • Somatostatinoma: A rare tumor that produces excess somatostatin, leading to diabetes, gallstones, and steatorrhea due to its inhibitory effects on various hormones and digestive enzymes.