Carcinoid syndrome

This page was reviewed under our medical and editorial policy by

Gagandeep Singh, MD, Liver and Pancreatic Surgeon, City of Hope | Duarte

This page was updated on June 9, 2023.

Carcinoid syndrome is a condition that may result when a neuroendocrine tumor releases specific chemicals into the patient’s bloodstream.

Neuroendocrine tumors (NETs) are rare, slow-growing neoplasms that develop from neuroendocrine cells, which are hormone-producing cells found throughout the body.

Research shows that about 10 percent of these NETs result in carcinoid syndrome.

What is carcinoid syndrome?

Carcinoid syndrome is a group of symptoms that may occur when active peptides and amines are released into the bloodstream by neuroendocrine tumors of the gastrointestinal (GI) tract, the respiratory tract, the liver and a few other organs.

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

Carcinoid syndrome symptoms

Some patients may experience just one symptom of carcinoid syndrome, while others develop several. Possible symptoms include those listed below.

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

Diarrhea: About half of carcinoid syndrome patients develop diarrhea.

Breathing issues or wheezing: Some patients may feel like they're experiencing asthma symptoms when experiencing 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 the patient's heart may occur, causing difficulty breathing, weakness and fatigue or a heart murmur. In serious cases, this may lead to congestive heart failure.

Carcinoid syndrome causes

Research into the exact cause of carcinoid syndrome is ongoing. In most instances, it occurs when neuroendocrine cells that produce serotonin and other hormonal substances spread to the liver.

Carcinoid syndrome risk factors

Carcinoid syndrome is rare. Approximately 27 per 1 million Americans are diagnosed with neuroendocrine tumors annually, with about 10 percent of these patients developing carcinoid syndrome, according to the National Organization for Rare Disorders. While the incidence of most cancers has plateaued, the prevalence of neuroendocrine tumors continues to go up. The most recent numbers reflect that over the last 40 years, the incidence has gone up sevenfold.

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

Age: Though people of any age may develop a neuroendocrine tumor, 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 care team will likely conduct a physical examination to rule out other causes. Additional testing may be necessary, such as those tests listed below.

5-HIAA urine tests measure the metabolism of serotonin in urine, which produces 5-HIAA. This level is higher in patients with carcinoid syndrome.

Blood tests look for the presence of hormones and other substances released by neuroendocrine tumors.

Tumor markers such as chromogranin A levels and others might be relevant indicators of the syndrome.

Imaging tests help visualize the cancer to identify a tumor’s location and find out whether it has metastasized. These include a computed tomography (CT) scan, magnetic resonance imaging (MRI) and a specialized positron emission tomography (PET) scan called a dotatate scan, which may help detect neuroendocrine tumors.

Endoscopy and bronchoscopy each use a thin, lighted tube with a camera on the end to peer inside the body. An endoscopy gives doctors a look at the GI tract and a bronchoscopy checks out the lungs. Endoscopic ultrasound may facilitate location and sampling of these tumors. 

Biopsy involves removing a small tissue sample to be examined under a microscope to confirm the diagnosis.

Carcinoid syndrome treatment

Treatment for carcinoid syndrome often involves the surgical removal of the primary tumor and debulking the metastatic burden when deemed feasible.

If surgery isn’t an option for neuroendocrine tumor treatment, the patient 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, including Imodium® (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 neuroendocrine 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.
Learn more about neuroendocrine tumor survival rates.

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