Understanding Carcinoid Tumor

Medically Reviewed by Brunilda Nazario, MD on December 20, 2011

Carcinoid tumors are a rare, slow-growing type of cancer that can be cured if caught early, but is difficult to diagnose.

Most carcinoid tumors start in the gut, including the intestines, appendix, rectum, colon, stomach, and pancreas. They account for about one-third of all tumors of the small intestine and almost 50% of all malignant tumors of the small intestine. Yet these tumors can also be found in the lungs, ovary, and elsewhere.

Carcinoid tumors are a type of neuroendocrine tumor, which means they come from cells of the nervous and endocrine system, and can produce hormones. When they secrete excess hormones such as histamine and serotonin, they can cause symptoms such as flushing, stomach cramps, and diarrhea. This is called carcinoid syndrome.

Like most other types of cancer, carcinoid tumors are most easily treated when found early. In fact, in the early stages they can often be completely cured through surgery. Most carcinoid tumors grow and spread very slowly. But because these tumors often don't cause any symptoms for many years, early detection can be tricky.

When carcinoid tumors do cause symptoms, they may be vague, or may be similar to symptoms of other medical conditions.

Some gastrointestinal carcinoid tumors can cause symptoms such as abdominal pain, constipation, bleeding, or cramping. The lung carcinoids can cause infection, pneumonia, or chronic cough.

Carcinoid tumors can also lead to two conditions: Carcinoid syndrome and Cushing's syndrome.

Symptoms of carcinoid syndrome include diarrhea, flushing of the skin, wheezing, shortness of breath, abdominal cramps, and heart palpitations.

Symptoms of Cushing's syndrome can include weight gain, muscle weakness, thinning of the skin, increased facial and body hair, high blood sugar, and high blood pressure.

"The biggest obstacle in diagnosing carcinoid tumors is not thinking of them," says Richard Warner, MD, professor of medicine at the Mount Sinai School of Medicine and medical director of the Carcinoid Cancer Foundation. "Because carcinoid tumors are not so common, doctors may not think of them as a possibility when they see these symptoms."

Researchers are still learning about carcinoid tumors and what causes them. There are a few known risk factors for carcinoid tumors, and most are not factors you can control or change.

  • Genetic syndromes. People with a rare genetic syndrome called Multiple Endocrine Neoplasia, type 1 (MEN1) have a higher risk of certain tumors, including carcinoid tumors. Those with a disease called neurofibromatosis type 1 are also at higher risk for developing carcinoid tumors.
  • Gender. Women may be at slightly higher risk of developing carcinoid tumors. Researchers aren't sure why.
  • Race. Gastrointestinal carcinoid tumors are more common in African-American men and women than in Caucasians. But lung carcinoid tumors are more common in Caucasians than in people of other races.
  • Stomach conditions. Those who have a stomach condition that reduces the amount of acid in the stomach and damages the stomach have a higher risk of carcinoid tumors in the stomach.
  • Smoking. Smokers may be more likely to have certain types of lung carcinoid tumors. A recent study in Europe also found that smoking may double the risk of having a carcinoid tumor in the small intestine. But more research is needed to confirm these results.

Because carcinoid tumors grow slowly, many are caught early, before they have had a chance to metastasize or cause symptoms. In many cases, they are found during routine tests or exams when looking for other problems.

"These tumors are often found by accident," says James Yao, MD, associate professor and deputy chair of the Department of Oncology at the University of Texas MD Anderson Cancer Center in Houston. "We may find them during a screening colonoscopy or endoscopy or because of abnormal results on a liver function test."

Sometimes the tumors are found because they are causing symptoms. If your doctor suspects a carcinoid tumor, there are a few different types of diagnostic tests to use.

  • Blood and urine tests. These simple tests are often a first step in diagnosing carcinoid syndrome. Doctors use these tests to look for the excess hormones and other substances that carcinoid tumors produce.
  • Imaging tests. Doctors may use imaging tests to take pictures of the inside of your body to locate tumors. These tests may include X-ray, CT scan, MRI, PET scan, or octreoscan. An octreoscan is especially helpful in finding carcinoid tumors. During the test, a small amount of radioactive material and a hormone-like substance that is attracted to carcinoid tumors are injected into the bloodstream. A few hours later, a special camera looks for any "hotspots" where these substances have collected.
  • Endoscopy. This is a type of test that uses a long flexible tube with a camera or ultrasound at the end to look for gastrointestinal tumors. Using various kinds of endoscopy, doctors can see almost all areas of the digestive tract, from the esophagus to the rectum.
  • Biopsy. Once the tumor has been found, your doctor may take a small piece of tissue from the tumor to look at it under a microscope. "A biopsy is essential in diagnosing carcinoid tumor," says Warner. "Until you examine the cells under a microscope you don't know for certain what type of tumor you're dealing with. It also helps us know what type of treatments the tumor will best respond to."

When carcinoid tumors are caught before they have spread, they can often be completely removed and cured by surgery. Once the tumors have spread to other areas, other types of treatments may also be used, either on their own or in combination with surgery. These treatments may include medication, chemotherapy, radiation therapy, and ablation, to destroy all or part of the tumor.

No matter when the tumors are found, the prognosis is better the earlier treatment is started. "Some doctors used think that because these tumors were so slow growing that it was better to wait until the tumors were causing problems to treat them," says Warner. "But we now know that surgery and other treatments work much better when done early. Early, aggressive treatment of carcinoid tumors leads to a much better outcome for patients."

Show Sources


Richard Warner, MD, professor of medicine, Mount Sinai School of Medicine; medical director, The Carcinoid Cancer Foundation.

National Cancer Institute web site: "Gastrointestinal Carcinoid Tumors Treatment: Patient Version."

American Cancer Society web site: "Gastrointestinal Carcinoid Tumors," "Lung Carcinoid Tumor." MedlinePlus web site, "Carcinoid Syndrome."

James Yao MD, associate professor and deputy chair, Department of Oncology, University of Texas, MD Anderson Cancer Center, Houston.

The Carcinoid Cancer Foundation web site: "A Review of Carcinoid Cancer."

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