Carcinoid syndrome

This page was reviewed under our medical and editorial policy by

Maurie Markman, MD, President, Medicine & Science.

This page was updated on February 28, 2022.

Neuroendocrine tumors (NETs) are rare, slow-growing cancers that develop from neuroendocrine cells, which are hormone-producing cells found throughout the body. The most common type of NET is the carcinoid tumor.

Research shows that about 10 percent of these NETs result in a condition called carcinoid syndrome, according to StatPearls Publishing. Carcinoid syndrome occurs when carcinoid tumors of the gastrointestinal (GI) tract, respiratory tract, ovaries, testicles, kidneys or liver release active peptides and amines into the bloodstream.

Carcinoid tumors of the appendix, small intestine, cecum and colon that metastasize to the liver will more often lead to carcinoid syndrome than tumors that originate elsewhere.

Carcinoid syndrome symptoms

The most common symptom of carcinoid syndrome is flushing of the face, which occurs in about 85 percent of patients with this disease, according to StatPearls. The face, neck and upper torso may become warm and dark pink to red in color for as little as 30 seconds to as long as 30 minutes.

Diarrhea and wheezing are also hallmark symptoms of carcinoid syndrome.

Stress, alcohol, certain foods and heavy exercise may exacerbate these and other symptoms, which include:

  • Extreme diarrhea, which may lead to malabsorption of nutrients
  • Angiomas (dilated blood vessels)
  • Bronchial spasms
  • Rapid heartbeat
  • Quick decreases in blood pressure (hypotension)
  • Changes in weight
  • Dehydration
  • Muscle and joint pain
  • Peptic ulcers

Over time, damage to the valves of your heart can occur, causing difficulty catching your breath, weakness and fatigue or a heart murmur. In serious cases, this can lead to congestive heart failure.

Carcinoid syndrome causes

Research into the exact cause of carcinoid syndrome is ongoing, In most instances, it occurs when carcinoid cells that produce serotonin and other hormonal substances spread to the liver. This spread (metastasis) prevents the liver from doing its typical task of eliminating these substances before they reach the bloodstream and cause symptoms.

Carcinoid syndrome risk factors

Carcinoid syndrome is rare. Approximately 27 per 1 million Americans are diagnosed with carcinoid tumors annually, with about 10 percent of these patients developing carcinoid syndrome, according to the National Organization for Rare Disorders.

The following risk factors may increase the likelihood of developing a carcinoid tumor.

  • Age: Though people of any age may develop carcinoid syndrome, it’s more likely to occur in middle age.
  • Race: Although all races may be affected, African-Americans are slightly more likely than others to develop carcinoid syndrome.
  • Family history: Having relatives with certain genetic conditions, such as multiple endocrine neoplasia type 1 (MEN 1), increases the risk.

Carcinoid syndrome diagnosis

If a patient is experiencing symptoms of carcinoid syndrome, the doctor will likely conduct a physical examination to rule out other causes. Additional testing may be necessary, such as:.

  • 5-HIAA urine test measures the metabolism of serotonin in urine, which produces 5-HIAA. This level is higher in patients with carcinoid syndrome.
  • Blood test looks for the presence of hormones and other substances released by carcinoid tumors.
  • Imaging tests help visualize the cancer to identify the tumor’s location and find out whether it has metastasized. These include a computed tomography (CT) scan (the most common imaging test used in diagnosis), an ultrasound or magnetic resonance imaging (MRI).
  • Endoscopy or bronchoscopy each uses a thin, lighted tube with a camera on the end to peer inside the body. An endoscopy looks at the GI tract and a bronchoscopy checks out the lungs.
  • Biopsy involves removing a tissue sample to check for signs of cancer.

Carcinoid syndrome treatment

Treatment for carcinoid syndrome often involves the surgical removal of the tumor that is causing the symptoms.

If surgery isn’t an option, you may undergo one of the following treatments:

Treatment of carcinoid syndrome involves managing its symptoms and may include one or more of the following:

  • Anti-diarrheal medications to treat extreme diarrhea as a result of carcinoid syndrome, includingImodium® (loperamide), Lomotil® (diphenoxylate-atropine) or Xermelo® (telotristat ethyl)
  • Changes to diet and/or medications, including avoiding certain foods that are high in serotonin or that trigger its release and stopping medications that may affect adrenaline or amine levels (patients should never stop taking medication without a doctor’s direction)
  • Peptide receptor radionuclide therapy (PRRT), which involves the injection of a radioactive substance that binds with the cells of the tumor, to shrink it and decrease symptoms
  • Somatostatin analogs (SSA) to prevent the production of serotonin and other hormones that cause carcinoid syndrome, thereby reducing symptoms; these include Sandostatin® (octreotide), Somatuline Depot® (lanreotide) and the Bynfezia Pen®, which delivers octreotide in short-acting doses

Carcinoid syndrome survival rates

Because carcinoid syndrome occurs with carcinoid tumors, the survival rate depends on the extent of the tumor. Rates are categorized based on whether the cancer is:

  • Localized, or hasn’t spread past its place of origin
  • Regional, or has spread to nearby tissues and lymph nodes 
  • Distant, or has metastasized farther to other areas of the body, such as the liver.

For gastrointestinal carcinoid tumors, the five-year survival rates are as follows, according to the American Cancer Society (ACS):

  • Localized gastrointestinal carcinoid tumors: 97 percent
  • Regional gastrointestinal carcinoid tumors: 95 percent
  • Distant gastrointestinal carcinoid tumors: 67 percent

For lung carcinoid tumors, the ACS has five-year survival rates for:

  • Localized lung carcinoid tumors: 98 percent
  • Regional lung carcinoid tumors: 87 percent
  • Distant lung carcinoid tumors: 58 percent

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