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