As mentioned above, gastrointestinal (GI) neuroendocrine tumors (carcinoids) and neuroendocrine cancers often do not cause any symptoms and may be found when looking for causes of other problems. But some do cause symptoms that may lead to their diagnosis.

Signs and symptoms of gastrointestinal carcinoid tumors

Most GI carcinoids grow slowly, causing vague symptoms that are more often caused by something else. When trying to figure out what's going on, doctors and patients are likely to explore other, more common possible causes first. This can delay a diagnosis, sometimes even for several years.

The symptoms a person develops from a GI carcinoid tumor often depend on where it is located. People with tumors/cancers in their appendix often don’t have symptoms. If it is discovered, it is often when they have their appendix removed during an operation for some other problem. If the tumor/cancer starts in the small intestine, it can sometimes lead to abdominal pain caused by kinking or blockage of the intestines. This pain can be mild and last for a couple of years or more before the carcinoid tumor is found. Often a tumor needs to grow fairly large before it causes intestinal blockage.

Sometimes, a carcinoid may cause intestinal bleeding. This can lead to anemia (low red blood cell counts) with fatigue and shortness of breath. These same problems can also occur with carcinoid tumors/cancers that start in the colon. Rectal neuroendocrine tumors/cancers are often found on routine exam, though they can cause pain and bleeding from the rectum.

Neuroendocrine tumors/cancers that develop in the stomach usually grow slowly and often do not cause symptoms. They are sometimes found during routine exam of the stomach by endoscopy (described later on in this section). Some can cause symptoms such as the carcinoid syndrome.

Carcinoid syndrome

In about 1 out of 10 cases, carcinoid tumors release enough hormone-like substances into the bloodstream to cause symptoms. This results in the carcinoid syndrome. Symptoms include facial flushing (redness and warm feeling), severe diarrhea, wheezing, and fast heartbeat. Many patients find that these symptoms are triggered by factors such as stress, heavy exercise, and drinking alcohol. Over a long time, these hormone-like substances can damage heart valves, causing shortness of breath, weakness, and a heart murmur (an abnormal heart sound). Some neuroendocrine tumors/cancers may produce ACTH (adrenocorticotropic hormone), a substance that causes the adrenal glands to make too many hormones. This can cause weight gain, weakness, high blood sugar (even diabetes), and increased body and facial hair.

Not all GI neuroendocrine tumors/cancers can cause the carcinoid syndrome. For example, rectal carcinoids usually do not make the hormone-like substances that cause these symptoms.

Most cases of carcinoid syndrome are seen when the cancer has already spread to other parts of the body. Normally, blood coming from the GI tract first flows through the liver, where substances made by GI carcinoid tumors are broken down before they can reach the rest of the body. This prevents carcinoid symptoms. But if the neuroendocrine cancer spreads outside the intestine (such as to the liver or lungs), the substances it makes can enter the main bloodstream and reach other parts of the body, where it can cause symptoms.

Medical history and physical exam

A medical history is an interview in which the doctor asks questions about symptoms and risk factors you may have. The doctor will probably ask about symptoms of the carcinoid syndrome, as well as symptoms that might be caused by a mass (tumor) in the stomach, intestines, or rectum.

Some patients with neuroendocrine tumors/cancers also have cancers or benign tumors of other organs, so doctors may ask about symptoms that might suggest other tumors are present. A thorough physical exam will provide information about signs of neuroendocrine tumors/cancers and other health problems. The doctor may pay special attention to the abdomen, looking for a tumor mass or enlarged liver.

If your medical history and physical exam give reason to suspect you may have a GI neuroendocrine tumor/cancer, the doctor will order some tests to find out if the disease is present.

Imaging tests

Your doctor may order one or more types of imaging tests to help determine the cause of your symptoms.

Barium x-rays

These studies use a barium-containing solution that coats the lining of the esophagus, stomach, and intestines. The coating of barium helps show up abnormalities of the lining of these organs. This type of study is often useful in diagnosing some GI carcinoid tumors. It is least effective in finding small intestine carcinoids. Barium studies can be used to examine the upper or lower parts of the digestive system. You will probably have to fast the night before the test. If the colon is being examined, you may need to take laxatives and/or enemas to cleanse the bowel the night before or the morning of these exams.

Barium swallow: This test (also known as an upper GI series) is used to examine the lining of the esophagus, stomach, and the first part of the small intestine. The patient drinks a barium solution and then x-ray pictures are taken. A small bowel follow through is a continuation of a barium swallow that is sometimes used to look for problems in the small intestine. For this test, x-rays are taken at regular intervals over the course of a few hours as the barium passes through the intestines.

Enteroclysis: This is another way to look at the small intestine. In this test, a thin tube is passed from the mouth or nose down through the stomach to the start of the small intestine. Barium contrast is sent through the tube, along with a substance that creates more air in the intestines, causing them to expand. X-rays of the intestines are then taken. This test may be quicker and give more complete results than a small bowel follow through, although placement of the tube can be uncomfortable, even when using medicine to numb the throat.

Barium enema: This test (also known as a lower GI series) is used to look at the inner surface of the large intestine. For this test, the barium solution is given as an enema (through the anus) while the patient is lying on the x-ray table. When the colon is about half full of barium, the patient rolls over so the barium spreads throughout the colon. Then x-rays are taken. After the barium is put in the colon, air may be blown in to help spread the barium toward the bowel wall and better coat the inner surface. This is called an air contrast (or double contrast) barium enema. X-rays are then taken.

Barium x-rays are used less these days than in the past. In many cases they are being replaced by endoscopy -- where the doctor actually looks into the colon or stomach with a narrow fiber optic scope.

Computed tomography

The computed tomography (CT) scan is an x-ray procedure that produces detailed cross-sectional images of your body. Instead of taking one picture, like a standard x-ray, a CT scanner takes many pictures as it rotates around you. A computer then combines these into images that look like slices of the part of your body that is being studied.

Before any pictures are taken, you may be asked to drink 1 to 2 pints of a liquid called oral contrast. This helps outline the intestine so that certain areas are not mistaken for tumors. You may also receive an IV (intravenous) line through which a different kind of contrast dye (IV contrast) is injected. This helps better outline structures in your body.

The injection can cause some flushing (redness and warm feeling that may last hours to days). A few people are allergic to the dye and get hives. Rarely, more serious reactions like trouble breathing and low blood pressure can occur. Medicine can be given to prevent and treat allergic reactions. Be sure to tell the doctor if you have ever had a reaction to any contrast material used for x-rays.

CT scans can help tell if your neuroendocrine tumor/cancer has spread into lymph nodes or other organs such as your liver. They can also be used to guide a biopsy needle precisely into a suspected area of cancer spread. For a CT-guided needle biopsy, the patient remains on the CT scanning table, while a doctor moves a biopsy needle in the body toward the location of the mass. CT scans are repeated until the doctor is confident that the needle is within the mass. A fine-needle biopsy sample (tiny fragment of tissue) or a core-needle biopsy sample (a thin cylinder of tissue about ½-inch long and less than 1/8-inch in diameter) is then removed and looked at under a microscope.

A CT scan takes longer than regular x-rays and you will need to lie still on a table while it is being done. You might feel a bit confined by the ring you lay within when the pictures are being taken.

Magnetic resonance imaging

Magnetic resonance imaging (MRI) scans use radio waves and strong magnets instead of x-rays. The energy from the radio waves is absorbed by the body and then released in a pattern formed by the type of tissue and by certain diseases. A computer translates the pattern into a detailed image of parts of the body. Like a CT scanner, this produces cross-sectional slices of the body. An MRI can produce slices that are parallel with the length of your body. As with a CT scan, a contrast material might be injected into a vein, but it is not needed as often.

MRI scans are a little more uncomfortable than CT scans. They take longer -- often up to an hour. You have to be placed inside tube-like equipment, which is confining and can upset people with a fear of enclosed spaces (claustrophobia). If this is a problem for you, let your doctor know before the scan. Sometimes medicine given before the MRI can help. You may also be given the option of having the scan at an "open" MRI machine. Open MRIs are less confining, but the images are not always as clear as with a regular MRI. Also, MRI machines make a buzzing noise that some people might find disturbing. Some places will provide headphones with music to block this sound.

Radionuclide scans

Scans using small amounts of radioactivity and special cameras may be helpful in looking for carcinoid tumors. They can help determine the extent of the tumor, as well as help locate it if doctors aren't sure where it is in the body.

Somatostatin receptor scintigraphy also known as OctreoScan: This is the most commonly used scan to look for carcinoid tumors. It uses a hormone-like substance called octreotide that has been bound to radioactive indium-111. Octreotide attaches to proteins on the carcinoid cells. A small amount of this substance is injected into a vein. It travels through the blood and is attracted to carcinoid tumors. About 4 hours after the injection, a special camera can be used to show where the radioactivity has collected in the body. More scans may be done on the following few days as well.

I-131 MIBG scan: This is another test that can be used to find carcinoid tumors. It is used less often than the OctreoScan. This test uses a chemical called MIBG to which radioactive iodine (I-131) is attached. This substance is injected into a vein, and the body is scanned several hours or days later with a special camera to look for areas that picked up the radioactivity. These would most likely be carcinoid tumors, although other kinds of neuroendocrine tumors will also pick up this chemical.

Positron emission tomography

A positron emission tomography (PET) scan is another imaging test that uses low levels of radioactivity to look for tumors. For most diseases, PET scans use a form of radiolabeled glucose (sugar) to find tumors. But when it is used to look for neuroendocrine tumors/cancers, PET uses a radioactive form of 5-hydroxytryptophan (5-HTP), a chemical that is taken up and used by carcinoid cells. A special camera can detect the radioactivity. Some doctors have found PET scans to be more accurate than CT scans for detecting spread of disease. However, this technique is not available in every hospital.

Endoscopy

These tests use a flexible lighted tube (endoscope) with a video camera on the end. The camera is connected to a monitor, which allows the doctor to see any masses in the lining of the digestive organs clearly. If abnormal areas are found, small pieces of tissue can be removed through the endoscope (biopsy). The tissue can be looked at under the microscope to find out if cancer is present and what kind of cancer it is.

Upper endoscopy (also known as an esophogogastroduodenoscopy or EGD): Patients are sedated (made sleepy) and the endoscope is passed down through the mouth to show the esophagus, stomach, and first part of the small bowel.

Colonoscopy (also known as a lower endoscopy): a special endoscope known as a colonoscope is inserted through the anus up into the colon. The colonoscope allows the doctor to see the lining of the entire rectum and colon. The colon has to be cleaned out before the test. This usually means drinking a large volume of a laxative solution the night before the exam. Sometimes an enema is also needed right before to make sure the bowels are empty. You will be given intravenous medicine to make you feel relaxed and sleepy during the procedure. A colonoscopy may be done in a hospital outpatient department, in a clinic, or in a doctor's office. It usually takes 15 to 30 minutes, although it may take longer if a tumor is seen and/or a biopsy taken.

Proctoscopy: Proctoscopy may be used to look for a rectal tumor. This involves using a shorter, hollow tube (a proctoscope), which is about 10 inches long and about 1 inch in diameter and may have a light on the end of it. The doctor coats the proctoscope with a lubricant and then gently pushes it into the anus and rectum. By shining a light into this tube, the doctor has a clear view of the lining of the rectum and anus. This test usually requires that you take laxatives or have an enema beforehand to make sure the bowels are empty.

Capsule endoscopy: Unfortunately, neither upper nor lower endoscopy can reach all areas of the small intestine, where many carcinoid tumors begin. This can delay finding these tumors. A technique known as capsule endoscopy may help in some cases. This test doesn't really use an endoscope. Instead, the patient swallows a capsule (about the size of a large vitamin pill) that contains a light source and a very small camera. Like any other pill, the capsule goes through the stomach and into the small intestine. As it travels (usually over the course of about 8 hours), it takes thousands of pictures. These images are transmitted electronically to a device worn around the person's waist, while he or she goes on with normal daily activities. The pictures can then be downloaded onto a computer, where the doctor can watch them as a video. The capsule passes out of the body during a normal bowel movement and is discarded. This is still a fairly new technique, and its use is still being studied.

Double balloon enteroscopy: This is another way to look at the small intestine. The small intestine is too long (20 feet) with too many curves to be examined well with regular endoscopy. This method gets around these problems by using a special endoscope that is made up of 2 tubes, one inside the other. First the inner tube, which is an endoscope, goes forward about a foot, and then a balloon at its end is inflated to anchor it. Then the outer tube goes forward to near the end of the inner tube and it is then anchored in place with a balloon. This process keeps being repeated over and over, letting the doctor see the intestine a foot at a time. This procedure is done after the patient is given drugs to make him or her sleepy. The main advantage of this test over capsule endoscopy is that the doctor can take a biopsy if something abnormal is seen.

Endoscopic ultrasound (EUS): This test uses an endoscope with a small ultrasound probe on the end. This probe releases sound waves and then detects the echoes that bounce off tissues of the digestive tract wall. A computer then translates the pattern of echoes into an image of the wall of the esophagus, stomach, intestine, or rectum. Putting the ultrasound probe on the end of an endoscope allows it to be placed very close to the tumor. This can allow for clearer pictures of some areas than you would get with a regular ultrasound (where the probe is on the outside of the body). By putting the ultrasound probe on the tip of the endoscope, it can get closer to the area where the tumor is to take pictures. Because the probe is close to the area being studied, it can make very detailed pictures. EUS can be used to see how deeply a tumor may have grown into the wall of the esophagus, stomach, intestine, or rectum. Endoscopic ultrasound can also help see if certain lymph nodes are enlarged and help a doctor guide a needle into a lymph node, tumor, or other suspicious area to do a biopsy.

Biopsy

Even if an imaging test finds a mass, it cannot tell if the mass is a carcinoid tumor, some other type of tumor or cancer, or an area of infection. The only way to know for sure is to remove cells from the abnormal area and look at them under a microscope. This procedure is called a biopsy.

There are several ways to take a sample from a gastrointestinal tumor. One way is through the endoscope. When a tumor is found, the doctor can use a biopsy forceps (pincers or tongs) through the tube to take a small sample of it. Another way to sample a tumor is with a CT-guided needle biopsy, as was described in the section on CT scans.

Bleeding after a biopsy from a neuroendocrine tumor/cancer is a rare but potentially serious problem. If bleeding becomes a problem, doctors can sometimes inject drugs into the tumor that constrict blood vessels to stop the bleeding.

In rare cases, neither an endoscopic biopsy nor a CT-guided needle biopsy will be able to get enough tissue to identify the type of tumor. This is sometimes the case with tumors in the small intestine. In such cases, a laparotomy (a surgical operation that opens the abdomen) to remove a tissue sample may be needed.

Blood and urine tests

Tests of the blood and urine can be very helpful in diagnosing carcinoid syndrome in patients who have symptoms that may be caused by it.

Serotonin (also called 5-HT) is a substance made by many carcinoid tumors, especially those in the small intestine. It is likely the cause of at least some of the symptoms of carcinoid syndrome. The body breaks it down into 5-hydroxyindoleactic acid (5-HIAA), which is released into the urine. A commonly used test to look for carcinoid syndrome measures the levels of 5-HIAA in a urine sample collected over 24 hours. Measuring the serotonin levels in the blood may also give useful information. These tests can help diagnose many (but not all) carcinoid tumors. In some cases, the tumors are small and don't release enough serotonin to result in a positive test. In other cases, the tumors do not make much serotonin, but they do make its precursor, 5-HTP. 5-HTP can be converted in the urine to serotonin. In patients with these tumors, the blood serotonin level may be normal, but the urine levels of serotonin and 5-HTP are high. Eating foods that contain a lot of serotonin can raise 5-HIAA levels in the urine. Such foods include, bananas, plantains, kiwi, certain nuts, and avocado. Medicines, including cough syrup and acetaminophen (Tylenol), can also affect the results. These substances should be avoided before urine and blood testing for carcinoids.

Other commonly used tests to look for carcinoids can include blood tests for chromogranin A (CgA), neuron-specific enolase (NSE), substance P, and gastrin. Depending on the where the tumor might be located and on the patient's symptoms, doctors may do other blood tests as well.

Some of these tests can also be used to show how well treatment is working, as the levels of these substances tend to go down as tumors shrink.

Last Medical Review: 06/19/2009
Last Revised: 06/19/2009