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, and the types of symptoms they cause
are often vague. When trying to figure out what's going on, doctors and
patients are likely to explore other, more common possible causes
first. This can lead to a delay in diagnosis, sometimes even for
several years.
The symptoms a person develops from a GI neuroendocrine tumor and
neuroendocrine cancer 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.
Sometimes, neuroendocrine tumors/cancers may cause intestinal bleeding.
The same is also true for carcinoid tumors/cancers that start in the
colon. These can grow fairly large, though, before causing intestinal
blockage. 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 are usually
slow growing and often do not cause symptoms. They are sometimes found
during routine exam of the stomach by endoscopy (see below). Some can
cause symptoms such as the carcinoid syndrome.
Carcinoid Syndrome
In about 1 out of 10 cases, neuroendocrine tumors/cancers 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 stress, heavy exercise, and
drinking alcohol may make these symptoms worse. 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, a substance that causes
the adrenal glands to make too many hormones. This can cause weight
gain, weakness, secondary 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 elsewhere
(including to the liver itself), the substances it makes can enter the
main bloodstream and reach other parts of the body, where it can cause
symptoms.
Exams and Tests Used to Diagnose GI
Carcinoid Tumors
If there is a reason to suspect you may have a GI neuroendocrine
tumor/cancer, the doctor will use one or more methods to find out if
the disease is present.
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 likely
ask about symptoms of the carcinoid syndrome, as well as symptoms that
might be caused by a mass 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.
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 find abnormalities of the lining of these organs. These are often
useful for the diagnosis of some GI carcinoid tumors. They are 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 and may need to take laxatives and/or enemas
to cleanse the bowel the night before or the morning of these exams.
A barium
swallow (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. Patients getting this test drink a barium
solution before the x-ray pictures are taken. A small bowel follow
through is a continuation of this test 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.
Another option for looking at the small intestine is
enteroclysis. In this test, a thin tube is passed from the mouth 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.
A barium enema
with air contrast (also known as double-contrast barium enema
or a lower GI
series) is used to look at the inner surface of the large intestine.
For this test, the barium solution is given 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. In addition to barium, air can be blown into the large intestine
to help push the barium towards the wall of this organ and better coat
its inner surface. 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 (CT)
The 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 an images of slices of
the part of your body that is being studied. Often after the first set
of pictures is taken you will get an intravenous (IV) injection of a
contrast agent, or dye, which helps better outline structures in your
body. A second set of pictures is then taken.
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.
CT scans take longer than regular x-rays. You need to lie
still on a table for 15 to 30 minutes while they are being done. But
they are getting faster, and your stay might be shorter. You might feel
a bit confined by the ring you lay within when the pictures are being
taken.
You may need an IV line through which the contrast dye is
injected. The injection can sometimes cause flushing. Some people are
allergic and get hives. Rarely, more serious reactions like trouble
breathing and low blood pressure can occur. Be sure to tell the doctor
if you have ever had a reaction to any contrast material used for
x-rays.
Magnetic Resonance Imaging (MRI)
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 used, 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. Newer, "open" MRI machines can help with this
if needed. The MRI machine makes a buzzing noise that some people may
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.
The most commonly used scan is somatostatin receptor
scintigraphy (SRS), also known as the OctreoScan. It
uses radioactive indium-111-lableled octreotide, a hormone-like
substance that attaches to carcinoid cells, which is bound to
radioactive indium-111. 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. Additional
scans may be done on the following few days as well.
Another test, known as an I-131
MIBG scan, is used less often. This test uses a chemical
called MIBG to which radioactive iodine (I-131) is attached. This 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
(PET)
A PET scan is another imaging test that uses low levels of
radioactivity to look for tumors. PET scanning for neuroendocrine
tumors/cancers uses a radioactive form of 5-hydroxytryptophan, 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 clearly see any masses in the lining of the
digestive organs. 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.
For upper
endoscopy (also known as an EGD), patients are sedated
(made sleepy) and a tube is passed down through the mouth to show the
esophagus, stomach, and first part of the small bowel.
In a colonoscopy
(also known as a lower endoscopy), a long-flexible tube 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. This test usually requires that you take laxatives or have
an enema beforehand 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.
For a suspected rectal tumor, a proctoscopy may be
done. 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.
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 newer technique, known as capsule endoscopy,
may help in some cases. For this test, a person 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.
Endoscopic Ultrasound
This is a fairly new technique used in some patients having
endoscopy. For this test, the endoscope has 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. Endoscopic ultrasound is
sometimes useful in determining how far a tumor has spread through the
wall of the esophagus, stomach, intestine, or rectum. The test can also
help predict whether the tumor has spread beyond the wall of these
organs to nearby tissues or lymph nodes.
Biopsy
Even if an imaging test finds a mass, it cannot tell if the
mass is a carcinoid tumor, some other type of tumor (benign or
cancerous), or a localized 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 involves opening
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 is a substance made by some carcinoid tumors,
especially those in the small intestine, and is likely the cause of
some of the symptoms. It is broken down by the body 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 or urine may also give useful
information. These tests can help diagnose some carcinoid tumors, but
they are not always 100% accurate. Some foods and medicines can affect
the results, and some small GI carcinoid tumors may not release enough
of these substances to result in a positive test.
Other commonly used tests to look for carcinoids can include
blood tests for chromogranin A (CgA), neuron-specific enolase (NSE),
and substance P. 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 Revised: 05/14/2007
|