Gastrointestinal Carcinoid Tumors

Gastrointestinal Carcinoid Tumors

Also called: Carcinoid Tumors, Carcinoid

Reviewed By:
Martin E. Liebling, M.D., FACP


Gastrointestinal carcinoid tumors are a rare form of cancer that develop in the gastrointestinal tract, which includes the stomach, small intestine and large intestine.

Gastrointestinal carcinoid tumors grow slowly and are highly treatable when caught at the earliest stages. However, patients with these tumors usually do not experience symptoms until the cancer has spread (metastasized), making it more difficult to detect these tumors until they have become more advanced.

The location and size of the tumor play a large role in determining whether or not it will spread. Very small tumors – less than 1 centimeter (about 1/2 inch) – usually do not spread, while larger tumors do. Because carcinoid tumors grow so slowly, patients whose cancer has spread may live for extended periods of time with the tumor.

Although gastrointestinal carcinoid tumors do not typically produce symptoms in their early stages, they sometimes produce mild abdominal pain if the tumors cause a bending or blockage of the intestines.

Early-stage gastrointestinal carcinoid tumors are sometimes discovered when a patient is being examined for another medical condition. However, a physician may suspect this type of tumor in patients who report persistent abdominal pain. Various imaging tests may be used to help diagnose this condition. Surgical removal of the tumor is the standard treatment for most gastrointestinal carcinoid tumors. In many cases, this is highly successful. In other cases, surgery or other treatments can only help relieve a patient’s symptoms. The prognosis is good for many patients with carcinoid tumors.

About gastrointestinal carcinoid tumors

Carcinoid tumors are a rare form of cancer that originate in the gastrointestinal tract. Occasionally, these tumors also develop in organs outside the digestive tract, such as the lungs. Carcinoid tumors develop slowly and are highly treatable when caught in the early stages of development.

Cancer can occur in any part of the gastrointestinal tract from the mouth to the rectum. Most cancers in the digestive tract occur in glandular tissues that produce mucus. Such cancers include stomach cancer and colorectal cancer. The tumors that develop in these areas are usually of the type called adenomas or adenocarcinomas.

Carcinoid tumors originate in the neuroendocrine cells, which are found in the digestive system and lungs. Neuroendocrine cells produce hormones that regulate the digestive juices and muscles that move food through the stomach and intestines. When these cells undergo certain changes, they may grow uncontrollably and form carcinoid tumors.  The majority of neuroendocrine cells are in the digestive system, so most carcinoid tumors develop there.

Within the digestive system, carcinoids occur most commonly in the small intestine, rectum and the appendix. They are the most common cancerous condition that affects the small intestine.  Gastrointestinal carcinoid tumors tend to grow slowly and may occur in multiple sites, especially when they are located within the small intestine.

The location and size of the tumor play a large role in determining whether or not a carcinoid tumor will spread. Very small tumors – 1 centimeter (about 1/2 inch) or less – usually do not spread (metastasize), although larger tumors frequently spread beyond their area of origin.

When detected early, gastrointestinal carcinoid tumors are usually treatable. However, they typically do not produce symptoms during their early stages of development and these early stage tumors may only be discovered as incidental findings, during abdominal surgery performed for other conditions. However, even when these tumors are not treated or removed, many patients may live for a long time because of the tumors’ slow growth. Gastrointestinal carcinoid tumors produce the same hormones as neuroendocrine cells. The hormones produced by tumors are usually destroyed by enzymes in the blood and liver. As long as the liver successfully breaks down these hormones, a patient usually experiences no symptoms related to the tumors. Many carcinoid tumors go undiagnosed because they progress slowly and may not cause readily identifiable symptoms during an individual’s lifetime.

However, in some cases, the tumors secrete excess hormones and produce varying symptoms. One collection of symptoms is called carcinoid syndrome and may affect breathing, skin and the circulatory system.

About 11,000 to 12,000 carcinoid tumors are diagnosed in the United States each year, according to the American Cancer Society. About half of these tumors are gastrointestinal carcinoids, and another third occur in the lungs. One-half of all gastrointestinal carcinoid tumors are found at an early stage of development.

Risk factors and causes

Little is known about the causes of gastrointestinal carcinoid tumors, although they are known to start out very small and spread very slowly.

Certain factors appear to increase the risk for developing gastrointestinal carcinoid tumors, including:

  • Family history of multiple endocrine neoplasia type 1 syndrome (MEN1 syndrome). This hereditary condition creates a high risk of developing tumors in the pituitary gland, parathyroid gland and pancreas. MEN1 syndrome is mostly like to cause carcinoid tumors in the stomach.
  • Conditions that affect the stomach’s production of stomach acid. These include atrophic gastritis, pernicious anemia or Zollinger-Ellison syndrome.
  • Smoking. A recent European study suggested that smoking may double the risk of developing carcinoid tumor of the small intestine.
  • Race. Carcinoid tumors are slightly more common among African Americans than Caucasians.
  • Age. Most carcinoid tumors are found in people above age 50, although carcinoid tumors in the appendix may be more common in younger adults.

Signs and symptoms

In most cases, gastrointestinal carcinoid tumors may not produce symptoms in their early stages. However, they may sometimes cause mild abdominal pain if the tumors cause a bending or blockage of the intestines. But this pain does not typically cause a person to seek medical help.

Usually, symptoms do not appear until the tumor has reached a more advanced stage. After it has spread, a patient may experience periodic abdominal pain or rarely gastrointestinal bleeding.

Some carcinoid tumors also produce excessive levels of adrenocorticotrophic hormone (ACTH), which stimulates the adrenal glands to secrete excessive levels of cortisol and other hormones. This can result in the following symptoms:

  • Weight gain
  • Weakness
  • Increased body and facial hair

Carcinoid syndrome occurs in about 10 percent of cases, according to the American Cancer Society. It may indicate that the cancer has spread to the liver, which usually breaks down substances released by the carcinoid tumors. Symptoms of this syndrome may include:

  • Facial flushing or feeling of warmth in the face and neck
  • Wheezing
  • Diarrhea
  • Rapid pulse
  • Severe drop in blood pressure
  • Small, benign skin tumors (angiomas)

Many patients find that these symptoms worsen during periods of stress, strenuous exercise or alcohol consumption. If substances secreted by the tumor are allowed to build up in the body over long periods of time, they may damage the heart valves.

Diagnosis of gastrointestinal carcinoid tumors

Because gastrointestinal carcinoid tumors do not typically cause symptoms in their early stages, these early-stage tumors may only be discovered when a patient is being examined for another condition. For example, they may be discovered during an appendectomy or when a patient is screened for colorectal cancer.

However, a physician may suspect gastrointestinal carcinoid tumors in cases of persistent abdominal pain. In diagnosing a gastrointestinal carcinoid tumor, a physician will perform a thorough physical examination and compile a comprehensive medical history. During the physical examination, the physician will look for the following symptoms:

  • Abdominal mass and enlarged liver
  • Prominent skin veins (telangiectasis)
  • Signs of carcinoid syndrome, including:

    • Heart murmur
    • Wheezing
    • Skin flushing

Gastrointestinal carcinoid tumors often produce excess levels of the hormone serotonin that may be detected during 24-hour urinary testing. The physician will look for elevated levels of 5-hydroxyindoleacetic acid (5HIAA), a metabolic product of serotonin, in the patient’s urine sample. Patients may be placed on a restricted diet prior to such testing because certain foods and medications can cause false positives.  Blood tests may also reveal the presence of certain hormones that may indicate carcinoid syndrome.

Imaging tests may also be used to examine the gastrointestinal tract and to look for signs of intestinal obstruction or spread of the cancer. These tests may include:

  • CAT scan. Uses multiple x-ray images, taken from different angles, and a computer to create three-dimensional images of internal body structures.
  • Radionuclide imaging. Test in which tiny amounts of radioactive materials (called “tracers”) are introduced into the patient’s body. The tracers emit a type of energy called gamma rays, which are detected by special devices and converted into images of internal body structures. A type of radionuclide scan called a somatostatin receptor scintigraphy (SRS) is used to locate carcinoid tumors. A PET scan is another type of radionuclide imaging test that may be used to identify spread of the disease.
  • X-ray. Creates an image of part of the body by using low doses of electromagnetic radiation. The patient may consume a barium liquid or food, or have a barium enema to create images of the digestive tract.
  • MRI. Produces clear cross-sectional or three-dimensional images of the body’s tissues, even through bone and other obstructions. This produces images similar to those of a CAT scan, but in greater detail.
  • Upper endoscopy. A thin, lighted tube called an endoscope is inserted through the mouth and esophagus into the stomach and the first part of the small intestine. This can be used to look for abnormalities in these areas.

  • Colonoscopy. A thin, lighted tube called a colonoscope is inserted through the rectum into the colon to search for abnormalities.

  • Biopsy. Removal of cells or tissues for laboratory analysis. Biopsies may be performed during an endoscopy or colonoscopy.

Because gastrointestinal carcinoid tumors spread so slowly, about one-half of these cancers are diagnosed at an early stage before the cancer has spread, according to the American Cancer Society.

Treatment and prevention

At this time, there is no known method for preventing gastrointestinal carcinoid tumors. However, it is believed that quitting smoking may reduce the risk of carcinoid tumors of the small intestine.

Surgical removal is the standard treatment for gastrointestinal carcinoid tumors. Even when tumors cannot be completely removed, surgery to remove portions of the tumor or to bypass intestinal obstructions may help relieve a patient’s symptoms. Such surgery can add years to a patient’s life, especially since carcinoid tumors tend to progress slowly.

A local excision may be performed to remove the tumor. This procedure is most effective when the tumor is at the localized stage. In this technique, the tumor and surrounding healthy tissue are surgically removed. In some cases, more extensive portions of nearby tissue may need to be removed.

Tumors may be surgically removed in a variety of procedures, depending on the location and size of the tumor. For example, small gastrointestinal carcinoid tumors in the stomach may be removed with the use of an endoscope. Larger tumors may require more invasive surgery.

Sometimes tumors may be destroyed rather than surgically removed. This can involve the use of needles or probes to apply electric current, radio waves or substances directly into the tumor cells. For example, electrofulguration may be used to deliver an electrical current that can heat and destroy small tumors in the rectum. Cancer that has spread to the liver may be treated through the injection of concentrated alcohol or liquid nitrogen to kill or freeze tumor cells. Some imaging tests may be used to help guide the needle during the procedure.

Additional treatment methods that may be used in patients with gastrointestinal carcinoid tumors include:

  • Chemotherapy. Drug treatment that targets fast-dividing cancer cells and kills them or interferes with their ability to reproduce and spread throughout the body. Carcinoid tumors are not very responsive to chemotherapy, so the treatment is usually reserved for tumors that have spread to other organs and are causing symptoms that have not responded to other medications.
  • Radiation therapy. Uses a specific type of radiation to kill or shrink cancer cells. Radiation may be used for carcinoid tumors when patients cannot withstand surgery, or to treat pain of metastasized tumors.
  • Biological therapy. Biological therapy drugs are medications that stimulate the body’s immune system to better recognize and attack cancer cells. Interferons may be used to shrink some carcinoid tumors that have spread.
  • Hormone therapy. Used to treat certain cancers that depend on hormones to grow and spread. Medications related to the hormone somatostatin may be used to treat carcinoid syndrome.

In some cases, palliative therapy may be recommended. Various drugs may be used to alleviate symptoms associated with carcinoid syndrome. These drugs rarely shrink tumors, but some can slow or stop the cancer’s growth. Other types of treatments for gastrointestinal carcinoid tumors are being tested in clinical trials.

Staging gastrointestinal carcinoid tumors

Determining the stage of gastrointestinal carcinoid tumors involves identifying the location and spread of cancer. This can help physicians identify the patient’s likely prognosis and select appropriate treatment or therapy.

Though there is no standard system for staging gastrointestinal carcinoid tumors, many physicians use a variation on the following model:

  • Localized stage. The tumor has not spread beyond the walls of the organ in which it developed (e.g., stomach, intestine, rectum).

  • Regional spread. The tumor has spread through the wall of the organ in which it developed and affects nearby tissues, which may include fat, ligaments, muscle and lymph nodes.

  • Distant spread. The tumor has spread to tissues or organs that are more distant from the organ in which the cancer developed. For example, a gastrointestinal carcinoid tumor may spread to the liver or bones.

The survival rates for these tumors depend on their organ of origin. For example, patients with tumors in the small intestine have a much higher survival rate than those with stomach tumors. According to the American Cancer Society, the five-year survival rate for patients diagnosed with gastrointestinal carcinoid tumors – at any stage – is 68 percent.

Questions for your doctor

Preparing questions in advance can help patients have more meaningful discussions with healthcare professionals regarding their condition. Patients may wish to ask their doctor the following questions related to gastrointestinal carcinoid tumors:

  1. Why do you think I may have a gastrointestinal carcinoid tumor?
  2. Could my signs or symptoms indicate another condition?
  3. What tests will you need to perform to confirm your diagnosis?
  4. When and from whom will I receive the test results?
  5. What is the stage of my gastrointestinal carcinoid tumor?
  6. How quickly is my gastrointestinal carcinoid tumor likely to progress?
  7. What symptoms of mine are likely to worsen over time?
  8. What are my treatment options?
  9. What are the risks and benefits of these treatments?
  10. Even if my tumor is completely removed, am I likely to experience more tumors in the future?
  11. Am I now at greater risk for other types of gastrointestinal cancers?
  12. What is my long-term prognosis?
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