Carcinoid syndrome occurs when a rare cancerous tumor called a carcinoid tumor secretes certain chemicals into your bloodstream, causing a variety of signs and symptoms. A carcinoid tumor, which is a type of neuroendocrine tumor, occurs most often in the gastrointestinal tract or the lungs.

Carcinoid syndrome typically occurs in people who have carcinoid tumors that are advanced. Treatment for carcinoid syndrome usually involves treating the cancer. However, because most carcinoid tumors don't cause carcinoid syndrome until they're advanced, a cure may not be possible. Medications may be recommended to relieve your carcinoid syndrome symptoms and make you more comfortable.

The signs and symptoms of carcinoid syndrome depend on which chemicals the carcinoid tumor secretes into your bloodstream.

The most common signs and symptoms include:

• Skin flushing. The skin on your face and upper chest feels hot and changes color — ranging from pink to purple. Flushing episodes may last from a few minutes to a few hours or longer.

  Flushing may happen for no obvious reason, though sometimes it can be triggered by stress, exercise or drinking alcohol.

• Facial skin lesions. Purplish areas of spiderlike veins may appear on your nose and upper lip.
• Diarrhea. Frequent, watery stools sometimes accompanied by abdominal cramps may occur in people who have 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.
• Rapid heartbeat. Periods of a fast heart rate could be a sign of carcinoid syndrome.

When to see a doctor

Make an appointment with your doctor if you have signs and symptoms that concern you.

Carcinoid syndrome is caused by a carcinoid tumor that secretes serotonin or other chemicals into your bloodstream. Carcinoid tumors occur most often in the gastrointestinal tract, including your stomach, small intestine, appendix, colon and rectum.

Only a small percentage of carcinoid tumors secrete the chemicals that cause carcinoid syndrome. When these tumors do secrete the chemicals, the liver normally neutralizes the chemicals before they have a chance to travel through your body and cause symptoms.

However, when an advanced tumor spreads (metastasizes) to the liver itself, it may secrete chemicals that aren't neutralized before reaching the bloodstream. Most people who experience carcinoid syndrome have an advanced cancer that has spread to the liver.

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 farther upstream from the liver, which then cannot process and eliminate the chemicals.

Carcinoid tumors in the intestine, on the other hand, secrete the 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.

Having carcinoid syndrome can cause the following complications:

• Carcinoid heart disease. Some people with carcinoid syndrome develop carcinoid heart disease. Carcinoid syndrome causes problems with 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. Carcinoid heart disease can eventually lead to heart failure. Surgical repair of damaged heart valves may be an option.

• Carcinoid crisis. Carcinoid crisis causes a severe episode of flushing, low blood pressure, confusion and breathing difficulty. Carcinoid crisis can occur in people with carcinoid tumors when they are exposed to certain triggers, including anesthetic used during surgery. Carcinoid crisis can be fatal. Your doctor may give you medications before surgery to reduce the risk of carcinoid crisis.

Your doctor will assess your signs and symptoms to rule out other causes of skin flushing and diarrhea. If no other causes are found, your doctor may suspect carcinoid syndrome.

To confirm a diagnosis, your doctor may recommend further tests, including:

• Urine test. Your urine may contain a 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 certain substances that are released by some carcinoid tumors.
• Imaging tests. Imaging tests may be used to locate the primary carcinoid tumor and determine whether it has spread. Your doctor may start with a CT scan of your abdomen, because most carcinoid tumors are found in the gastrointestinal tract. Other scans, such as MRI or nuclear medicine scans, may be helpful in certain situations.

• A scope or camera to see 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. A bronchoscopy, which uses 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.

• 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.

Treating carcinoid syndrome involves treating your cancer and may also involve using medications to control your specific signs and symptoms.

Treatments may include:

• Surgery. Surgery to remove your cancer or most of your cancer may be an option.
• Medications to block cancer cells from secreting chemicals. Injections of the medications octreotide (Sandostatin) and lanreotide (Somatuline Depot) may reduce the signs and symptoms of carcinoid syndrome, including skin flushing and diarrhea. A drug called telotristat (Xermelo) can be combined with these drugs to control diarrhea caused by carcinoid syndrome.
• Drugs that deliver radiation directly to the cancer cells. Peptide receptor radionuclide therapy (PRRT) combines a drug that seeks out cancer cells with a radioactive substance that kills them. In PRRT for carcinoid tumors, the drug is injected into your body, where it travels to the cancer cells, binds to the cells and delivers the radiation directly to them. This therapy is used in people who have advanced cancer that hasn't responded to other treatments.
• Stopping blood supply to liver tumors. 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 injects particles designed to clog the hepatic artery, cutting off the blood supply to cancer cells that have spread to the liver. The healthy liver cells survive by relying on blood from other blood vessels.
• Killing cancer cells in the liver with heat or cold. Radiofrequency ablation delivers heat through a needle to the cancer cells in the liver, causing the cells to die. Cryotherapy is similar, but it works by freezing the tumor.
• Chemotherapy. Chemotherapy uses strong drugs to kill cancer cells. Chemotherapy drugs can be given through a vein (intravenously) or in pill form, or both methods can be used.

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 skin flushing. Certain substances or situations, such as alcohol or large meals, can trigger flushing. Keep track of what causes your flushing, and try to avoid those triggers.
• Consider taking a multivitamin. Chronic diarrhea makes it difficult for your body to process the vitamins and nutrients in the food you eat. Ask your doctor whether taking a multivitamin may be a good idea for you.

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 be stressful. As you develop your way of coping with a cancer diagnosis, talk with your health care team about how you feel and consider trying to:

• Find out enough about carcinoid syndrome to make decisions about your care. Ask your doctor questions about your condition. Ask members of your health care team to recommend resources where you can get more information.

  Knowing about your condition may enable you to better 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 those 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 or online.

• Take care of yourself. Do what you can to maintain a healthy lifestyle. Eat a diet full of fruits and vegetables. When you feel up to it, include light exercise in 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.

You may start by seeing your family doctor if you have signs and symptoms of carcinoid syndrome. Depending on what your doctor finds, you may be referred to a doctor who specializes in treating cancer (oncologist), a specialist in disorders of the endocrine system (endocrinologist) or a surgeon.

Because appointments can be brief, and because there's often a lot to discuss, it's a good idea to be prepared. Here's some information to help you get ready, and know what to expect from your doctor.

What you can do

• Be aware of any pre-appointment restrictions. At the time you make the appointment, be sure to ask if there's anything you need to do in advance, such as restrict your diet.
• Write down any symptoms you're experiencing, including any that may seem unrelated to the reason for which you scheduled the appointment.
• Write down key personal information, including any major stresses or recent life changes.
• Make a list of all medications, vitamins or supplements that you're taking.
• Consider taking a family member or friend along. Sometimes it can be difficult to remember all the information provided during an appointment. Someone who accompanies you may remember something that you missed or forgot.
• Write down questions to ask your doctor.

Your time with your doctor is limited, so preparing a list of questions can help you make the most of your time together. List your questions from most important to least important in case time runs out. For carcinoid syndrome, some basic questions to ask your doctor include:

• What is likely causing my symptoms or condition?
• Other than the most likely cause, what are other possible causes for my symptoms or condition?
• What kinds of tests do I need?
• Is my condition likely temporary or chronic?
• What is the best course of action?
• What are the alternatives to the primary approach that you're suggesting?
• I have other health conditions. How can I best manage them together?
• Are there any restrictions that I need to follow?
• Should I see a specialist? What will that cost, and will my insurance cover it?
• Is there a generic alternative to the medicine you're prescribing me?
• Are there brochures or other printed material that I can take with me? What websites do you recommend?
• What will determine whether I should plan for a follow-up visit?

In addition to the questions that you've prepared to ask your doctor, don't hesitate to ask other questions as they occur to you.

What to expect from your doctor

Your doctor is likely to ask you a number of questions. Being ready to answer them may allow time later to cover other points you want to address. Your doctor may ask:

• When did you first begin experiencing symptoms?
• Have your symptoms been continuous or occasional?
• How severe are your symptoms?
• What, if anything, seems to improve your symptoms?
• What, if anything, appears to worsen your symptoms?