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.
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 a condition called carcinoid syndrome. Carcinoid syndrome occurs when active peptides and amines are released into the bloodstream by tumors of the gastrointestinal (GI) tract, the liver and a few other organs.
Neuroendocrine 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. 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 neuroendocrine cells that produce serotonin and other hormonal substances spread to the liver.
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 incidence 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.
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 primary tumor and debulking the metastatic burden when deemed feasible.
If surgery isn’t an option, 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:
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:
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: