Carcinoid tumor

Last updated: March 22, 2022

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Carcinoids are small, slow-growing neuroendocrine tumors. They are most commonly located in the gastrointestinal tract and can synthesize a variety of hormones (especially serotonin). Most carcinoids are asymptomatic because most of the hormones they produce are metabolized by the first-pass effect in the liver. Carcinoid syndrome – characterized by diarrhea, flushing, dyspnea, and wheezing – may occur if a serotonin-producing tumor has metastasized to the liver, bypassing first-pass metabolism. Elevated 5-HIAA in the urine helps to establish the diagnosis. Imaging techniques such as CT, MRI, and somatostatin receptor scintigraphy are used to detect the primary tumor as well as its metastases. Surgical resection is the first-line treatment. In inoperable cases, somatostatin analogs can be given.

Epidemiological data refers to the US, unless otherwise specified.

Overview [2]

Tumor location [2]

Secretory products [2]

The Measure of thirds for carcinoid tumors: are Multiple, are associated with another Malignancy, Metastasize.

In a patient presenting with secretory diarrhea, episodic flushing, wheezing, and cardiac valvular abnormalities, consider a carcinoid tumor.

Carcinoid lung tumor

Ovarian strumal carcinoid [5]


  • Clinical biochemistry should be performed first if a carcinoid tumor is suspected.
  • Imaging tests are then used to localize and stage the tumor.

Clinical biochemistry


Biopsy [6]

Neuroendocrine tumors

Differential diagnosis of carcinoid tumor
Blood glucose Diarrhea Associated conditions Other findings
Carcinoid tumor
  • Normal
  • Yes (watery)
  • Sometimes
  • No
  • Normal
  • Slightly ↑
  • No

Other differential diagnoses

The differential diagnoses listed here are not exhaustive.

Operable disease

Surgical resection

Inoperable disease

  1. Zuetenhorst JM, Taal BG. Metastatic carcinoid tumors: a clinical review. The Oncologist. 2005; 10 (2): p.123-31. doi: 10.1634/theoncologist.10-2-123 . | Open in Read by QxMD
  2. Ha J, WA Tan. Gastrointestinal Carcinoid Tumours: A Review. Journal of Gastrointestinal & Digestive System. 2012; 2 (2). doi: 10.4172/2161-069X.1000107 . | Open in Read by QxMD
  3. Shah GM, Shah RG, Veillette H et al.. Biochemical assessment of niacin deficiency among carcinoid cancer patients. American Journal of Gastroenterology. 2005; 100 (10): p.2307-14. doi: 10.1111/j.1572-0241.2005.00268.x . | Open in Read by QxMD
  4. Fox DJ, Khattar RS. Carcinoid heart disease: presentation, diagnosis, and management. Heart. 2004; 90 (10): p.1224-8. doi: 10.1136/hrt.2004.040329 . | Open in Read by QxMD
  5. Antovska VS, Trajanova M, Krstevska I, Gosheva I, Chelebieva J, Prodanova I. Ovarian Strumal Carcinoid Tumour: Case Report.. Open access Macedonian journal of medical sciences. 2018; 6 (3): p.540-543. doi: 10.3889/oamjms.2018.138 . | Open in Read by QxMD
  6. Carcinoid Tumor. Updated: February 23, 2018. Accessed: June 21, 2018.

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