Carcinoid Syndrome in
Neuroendocrine Tumors (NETs)

Carcinoid syndrome is a group of symptoms that may present in some patients when they have a specific type of cancer called a neuroendocrine tumor (NET). NETs are a rare, slow-growing type of cancer and can occur in any number of places in the body, most often in the gastrointestinal tract.

Clinical manifestations

Not all NETs cause carcinoid syndrome, but it can develop if the NET spreads from the small bowel (or other locations) to the liver. In these cases, the hormones the NET secretes cannot be filtered out by the liver as they normally would, so they get into the body’s circulatory system and cause the symptoms of carcinoid syndrome.

Carcinoid syndrome manifests with a range of symptoms, most notably flushing (experienced by 85% of patients), characterized by sudden reddening of the skin with a burning sensation, lasting from seconds to minutes and triggered by various stimuli. Diarrhea (experienced by 85% of patients) is another common and debilitating symptom, ranging in frequency and urgency, and often accompanied by cramping. Other symptoms and signs include:

Bronchospasm (wheezing and shortness of breath)
Venous telangiectasia (spider veins)
Cardiac valvular lesions

Timely diagnosis is challenging

Accurately diagnosing NETs is challenging. Contributing to the difficulty in diagnosis is the fact that NETs grow quite slowly, typically over a period of several years.

Someone may see a variety of health care providers, including specialists, over the course of several years before finally getting a proper diagnosis.

The occurrence of episodic facial flushing and/or severe watery diarrhea should lead to suspicion of carcinoid syndrome. Definitive diagnosis, however, is best achieved with a multimodal approach, which may include biochemical testing for 5-HIAA, a metabolite of serotonin, radiological or nuclear imaging, and tissue biopsy.

The burden on patient lives

Many of the major symptoms of carcinoid syndrome tend to be severe, including spontaneous onset of flushing episodes, during which some patients report “feeling on fire.” Frequent diarrhea can hit anytime, anywhere. Additionally, difficulty breathing can induce a panicked feeling.

These daily challenges often cause a great deal of stress for patients. Not knowing where, why, or when the next episode will hit can severely inhibit social interaction, which can lead to a sense of isolation. In undiagnosed patients, these episodes can cause alarm for one’s health and can lead to frustration if not recognized for what they are.

Resources for patients and their families

We encourage you to establish connections with the following organizations to continue raising your awareness so that these vastly underserved patients can realize brighter futures.