Carcinoid syndrome occurs when a rare cancerous tumor called a carcinoid tumor secretes serotonin and other chemicals into your bloodstream, causing a variety of signs and symptoms. Carcinoid tumors occur most commonly in the gastrointestinal tract, including the stomach, small intestine, appendix, colon and rectum, or in the lungs. In rare circumstances, carcinoid tumors can develop in the ovaries.

Because carcinoid tumors generally grow slowly, they typically don't cause signs and symptoms until quite advanced. You might discover you have carcinoid cancer through a test for an unrelated disease or condition.

Treatment for carcinoid syndrome usually involves treating your cancer. However, because most carcinoid tumors don't cause carcinoid syndrome until they're very advanced, a cure may not be possible. In those cases, medications may relieve the signs and symptoms of carcinoid syndrome and make you more comfortable.

The signs and symptoms you have will depend on what chemicals your carcinoid tumor secretes into your bloodstream. The most common signs and symptoms include:

• Skin flushing. The skin on your face and upper chest changes color — ranging from pink to red to purple. Flushing episodes last 20 to 30 seconds and make your skin feel hot. Flushing may happen for no obvious reason, though sometimes it can be provoked by eating or drinking alcohol.
• Facial skin lesions. Purplish areas of spider-like veins may appear on the noses and upper lips of people who've had carcinoid syndrome for many years.
• Diarrhea. Frequent, watery stools accompanied by painful abdominal cramps may signal carcinoid syndrome.
• Difficulty breathing. Asthma-like signs and symptoms, such as wheezing and shortness of breath, may occur at the same time you experience skin flushing.

Carcinoid syndrome is caused by a carcinoid tumor that secretes chemicals into your bloodstream. A small percentage of carcinoid tumors secrete chemicals. Some carcinoid tumors secrete chemicals, but your liver effectively processes the chemicals before they have a chance to travel through your body and cause signs and symptoms. Most people who experience carcinoid syndrome have an advanced tumor that has spread to the liver, where tumors have a better chance of secreting chemicals into the bloodstream.

Some carcinoid tumors don't have to be advanced to cause carcinoid syndrome. For instance, carcinoid lung tumors that secrete chemicals into the blood do so much farther upstream — not directly into the liver, where the chemicals are processed and weakened. Carcinoid tumors in the intestine, on the other hand, secrete their chemicals into blood that must first pass through the liver before reaching the rest of the body. The liver usually neutralizes the chemicals before they can affect the rest of the body.

What causes carcinoid tumors is unclear.

Only people with carcinoid tumors are at risk of carcinoid syndrome. People with carcinoid tumors are more likely to experience carcinoid syndrome if they:

• Have a gastrointestinal carcinoid tumor
• Have a carcinoid tumor that has spread (metastasized) to the liver

Make an appointment with your doctor if you believe you have signs and symptoms of carcinoid syndrome.

Tell your doctor about your signs and symptoms. He or she will want to rule out other causes of flushing and diarrhea. If no other causes are found, your doctor may suspect carcinoid syndrome. To confirm your diagnosis, your doctor may recommend further tests, including:

• Urine test. Your urine may contain a certain substance made when your body breaks down serotonin. An excess amount of this substance could indicate that your body is processing extra serotonin, the chemical most commonly excreted by carcinoid tumors.
• Blood test. Your blood may contain high levels of the protein chromogranin A, which is released by some carcinoid tumors.

Your doctor may conduct other tests and imaging procedures to diagnose carcinoid syndrome. Imaging tests may also be used to locate the primary tumor and determine whether it has spread. Your doctor may start with a computerized tomography (CT) scan of your abdomen, since most carcinoid tumors are in the gastrointestinal tract. Other tests may be necessary.

People with carcinoid syndrome are at risk of the following complications:

• Carcinoid heart disease. Some people with carcinoid syndrome develop carcinoid heart disease. Carcinoid syndrome causes a thickening of the heart valves, making it difficult for them to function properly. As a result, the heart valves may leak. Signs and symptoms of carcinoid heart disease include fatigue and shortness of breath during physical activity. Carcinoid heart disease can eventually lead to heart failure. Your doctor may recommend medications for your heart. Surgical repair of damaged heart valves is the only treatment to correct carcinoid heart disease.
• Bowel obstruction. Cancer that spreads to the lymph nodes adjacent to your small intestine can cause narrowing and kinking of your intestine, leading to a bowel obstruction. Signs and symptoms of a bowel obstruction include severe, cramping abdominal pain and vomiting. Surgery may be necessary to relieve the obstruction.
• Carcinoid crisis. Carcinoid crisis causes a severe episode of flushing, low blood pressure, confusion and breathing difficulty. Triggers include anesthesia, chemotherapy and other cancer treatments, though carcinoid crisis can occur for no apparent reason. Carcinoid crisis can be fatal. Your doctor may give you medications before surgery or chemotherapy to reduce the risk of carcinoid crisis.

Treating carcinoid syndrome involves treating your cancer. Surgery to remove your cancer or most of your cancer may be an option. If surgery isn't an option because your cancer is too widespread, your doctor may recommend treatment to shrink your tumors. This may reduce the signs and symptoms of carcinoid syndrome.

Treatments could include:

• Octreotide (Sandostatin). Monthly octreotide injections may slow the rate of growth of your carcinoid tumor and reduce the signs and symptoms of carcinoid syndrome. Octreotide controls flushing and diarrhea in most people with carcinoid syndrome. Side effects of octreotide include abdominal pain and bloating, diarrhea and nausea, though these symptoms may subside with time. Some people can't tolerate the side effects of octreotide and must stop taking the drug.
• Stopping blood supply to the tumor. In a procedure called hepatic artery embolization, a doctor inserts a catheter through a needle near your groin and threads it up to the main artery that carries blood to your liver (hepatic artery). The doctor releases particles to clog the hepatic artery, cutting off the blood supply to any cancer cells that have spread to the liver. The healthy liver cells survive by relying on blood from other blood vessels. Hepatic artery embolization can be risky, especially in people with liver disease, and the procedure is typically only performed in specialized medical centers. Discuss the benefits and risks with your doctor.
• Killing cancer cells with heat. Radiofrequency ablation delivers heat through a needle to the cancer cells in the liver, causing the cells to die. Radiofrequency ablation might be an option if you have a small number of liver metastases that are small in size. Radiofrequency ablation is generally safe, though there is a small risk of blood loss and infection.
• Chemotherapy. Chemotherapy drugs may shrink carcinoid tumors. What side effects you may experience will depend on which chemotherapy drugs you receive. Discuss your particular chemotherapy regimen with your doctor.

Medications to control your specific signs and symptoms also may be available. Your doctor may try various combinations of medications to treat your signs and symptoms based on the specific characteristics of your cancer.

The prognosis for people living with carcinoid cancer varies widely, depending on the extent of tumor spread and whether carcinoid syndrome has developed. As cancer research continues, doctors are finding new ways to treat advanced cancers, which may improve survival.

Talk to your doctor about self-care measures that may improve your signs and symptoms. Self-care measures can't replace treatment, but they may complement it. Ask your doctor if you should:

• Avoid things that cause flushing. Certain substances or situations can trigger flushing, such as alcohol or large meals. Some people experience flushing when they're feeling stressed or upset. Keep track of what causes your flushing and try to avoid situations that could trigger flushing.
• Eat a low-fat diet. A low-fat, high-protein diet may help relieve your diarrhea.
• Consider taking a multivitamin. Chronic diarrhea makes it difficult for your body to process the vitamins and nutrients in the food you eat. Your doctor might recommend a multivitamin to supplement your diet. Don't take any vitamins or other dietary supplements without first consulting your doctor.

You may be relieved to finally find an answer to what's been causing your signs and symptoms, but a diagnosis of a rare disease such as carcinoid syndrome can also be scary and stressful. Everyone has his or her own way of coping with a cancer diagnosis. If you aren't sure what to do next, talk with your health care team about how you feel and consider trying to:

• Find out all you can about carcinoid syndrome. Ask your doctor questions about your condition. Ask members of your health care team to recommend resources where you can get more information. The more you know about your condition, the better you're able to participate in decisions about your care.
• Talk to other people with carcinoid syndrome. Support groups for people with carcinoid syndrome put you in touch with people who have faced the same challenges you are facing. Ask your doctor about groups in your area. Carcinoid syndrome is rare, though, so you may need to connect with people outside your immediate area.
• Take care of yourself. Do what you can to maintain a healthy lifestyle. Choose healthy meals with plenty of fruits and vegetables. When you feel up to it, work light exercise into your daily routine. Cut extra stress out of your life when possible. Get plenty of sleep so that you feel rested when you wake up. Take care of your body and mind so that you're better able to stick to your cancer treatment plan.