Carcinoid tumors are a type of slow-growing cancer that can arise in several places throughout your body. Carcinoid tumors, which are one subset of tumors called neuroendocrine tumors, usually begin in the digestive tract (stomach, appendix, small intestine, colon, rectum) or in the lungs.

Carcinoid tumors often don’t cause signs and symptoms until late in the disease. Carcinoid tumors can produce and release hormones into your body that cause signs and symptoms such as diarrhea or skin flushing.

Treatment for carcinoid tumors usually includes surgery and may include medications.

In some cases, carcinoid tumors don’t cause any signs or symptoms. When they do occur, signs and symptoms are usually vague and depend on the location of the tumor.

Signs and symptoms of carcinoid lung tumors include:

• Chest pain
• Wheezing
• Shortness of breath
• Diarrhea
• Redness or a feeling of warmth in your face and neck (skin flushing)
• Weight gain, particularly around the midsection and upper back
• Pink or purple marks on the skin that look like stretch marks

Signs and symptoms of carcinoid tumors in the digestive tract include:

• Abdominal pain
• Diarrhea
• Nausea, vomiting and inability to pass stool due to intestinal blockage (bowel obstruction)
• Rectal bleeding
• Rectal pain
• Redness or a feeling of warmth in your face and neck (skin flushing)

It’s not clear what causes carcinoid tumors. In general, cancer occurs when a cell develops mutations in its DNA. The mutations allow the cell to continue growing and dividing when healthy cells would normally die.

The accumulating cells form a tumor. Cancer cells can invade nearby healthy tissue and spread to other parts of the body.

Doctors don’t know what causes the mutations that can lead to carcinoid tumors. But they know that carcinoid tumors develop in neuroendocrine cells.

Neuroendocrine cells are found in various organs throughout the body. They perform some nerve cell functions and some hormone-producing endocrine cell functions. Some hormones that are produced by neuroendocrine cells are cortisol, histamine, insulin and serotonin.

Factors that increase the risk of carcinoid tumors include:

• Older age. Older adults are more likely to be diagnosed with a carcinoid tumor than are younger people or children.
• Women are more likely than men to develop carcinoid tumors.
• Family history. A family history of multiple endocrine neoplasia, type I (MEN I), increases the risk of carcinoid tumors. In people with MEN I, multiple tumors occur in glands of the endocrine system.

The cells of carcinoid tumors can secrete hormones and other chemicals, causing a range of complications, including:

Carcinoid syndrome. Carcinoid syndrome causes redness or a feeling of warmth in your face and neck (skin flushing), chronic diarrhea, and difficulty breathing, among other signs and symptoms.

Carcinoid heart disease. Carcinoid tumors may secrete hormones that can cause thickening of the lining of heart chambers, valves and blood vessels. This can lead to leaky heart valves and heart failure that may require valve-replacement surgery. Carcinoid heart disease can usually be controlled with medications.

Cushing’s syndrome. A lung carcinoid tumor can produce an excess of a hormone that can cause your body to produce too much of the hormone cortisol.

Tests and procedures used to diagnose carcinoid tumors include:

• Blood tests. If you have a carcinoid tumor, your blood may contain high levels of hormones secreted by a carcinoid tumor or byproducts created when those hormones are broken down by the body.
• Urine tests. People with carcinoid tumors have excess levels of a chemical in their urine that’s produced when the body breaks down hormones secreted by carcinoid tumors.
• Imaging tests. Imaging tests, including a computerized tomography (CT) scan, magnetic resonance imaging (MRI), positron emission tomography (PET), octreotide scan and X-ray, may help your doctor pinpoint the carcinoid tumor’s location.
• A scope or camera that sees inside your body. Your doctor may use a long, thin tube equipped with a lens or camera to examine areas inside your body.

An endoscopy, which involves passing a scope down your throat, may help your doctor see inside your gastrointestinal tract. Bronchoscopy, using a scope passed down your throat and into your lungs, can help find lung carcinoid tumors. Passing a scope through your rectum (colonoscopy) can help diagnose rectal carcinoid tumors.

To see inside your small intestine, your doctor may recommend a test using a pill-sized camera that you swallow (capsule endoscopy).

• Removing tissue for laboratory testing. A sample of tissue from the tumor (biopsy) may be collected to confirm your diagnosis. What type of biopsy you’ll undergo depends on where your tumor is located.

In some cases a surgeon may use a needle to draw cells out of the tumor. In other cases, a biopsy may be collected during surgery. The tissue is sent to a laboratory for testing to determine the types of cells in the tumor and how aggressive those cells appear under the microscope.

Treatment for a carcinoid tumor depends on the tumor’s location, whether cancer has spread to other areas of the body, the types of hormones the tumor secretes, your overall health and your own preferences.

When detected early, a carcinoid tumor may be removed completely using surgery. If carcinoid tumors are advanced when discovered, complete removal may not be possible. In some cases, surgeons may try to remove as much of the tumor as possible, to help control signs and symptoms.

Medications used to treat carcinoid syndrome include:

• Drugs that block cancer cells from secreting hormones.Using medications to block hormones secreted by the tumor may reduce the signs and symptoms of carcinoid syndrome and slow tumor growth.

Octreotide are given as injections under the skin. Side effects from either medication may include abdominal pain, bloating and diarrhea.

• Drugs to boost the immune system. An injectable medication called interferon alfa (Intron A, Pegasys, others), which stimulates the body’s immune system to attack the tumor, is sometimes used to slow the growth of carcinoid tumors and to relieve symptoms. Interferon can cause significant side effects, including fatigue and flu-like symptoms.

Carcinoid tumors commonly spread (metastasize) to the liver. Options for treatment may include:

• Liver surgery. Surgery to remove part of the liver (hepatic resection) may control signs and symptoms caused by liver tumors.
• Stopping blood supply to liver tumors.In a procedure called hepatic artery embolization, a doctor clogs the liver’s main artery (hepatic artery), cutting off the blood supply to cancer cells that have spread to the liver. Healthy liver cells survive by relying on blood from other blood vessels.

Killing cancer cells with heat or cold. Radiofrequency ablation delivers heat treatments that cause carcinoid tumor cells in the liver to die. Cryoablation uses cycles of freezing and thawing to kill cancer cells.