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Overall Diagnostic Approach
Most suspected cancers of children and adults can be found by
a physical examination and imaging tests. But treatment is usually not
begun until the diagnosis is confirmed by a biopsy (removal of a tissue
sample from the tumor for examination under a microscope).
Retinoblastoma is an important exception to that rule for 2
reasons. First, retinoblastoma can be recognized with great accuracy by
doctors who have experience with this disease, and it is unlikely to be
confused with other eye problems of children. Second, taking a biopsy
specimen from the tumor cannot be easily done without harming the eye
and risking disseminating (spreading) the tumor outside of the eye.
Signs and Symptoms
Retinoblastomas first come to attention because a parent or
pediatrician notices a child’s eye has an unusual appearance. Normally
when a light is shone in a child's eye, the pupil looks red because the
color of the light is changed by blood in vessels in the back of the
eye. If instead the pupil appears white, this is cause for concern.
This is often the earliest sign detected by most parents and the most
common reason a doctor’s help is sought. Often times, this white glare
of the eye is only seen after a flash photograph is taken.
Sometimes both eyes do not appear to look in the same
direction, a condition that doctors call strabismus
often called “lazy eye.” There are many possible causes of this in
children. Most of the time lazy eye is caused by mild weakness of the
muscles that control the eyes, but retinoblastoma is also one of the
rare causes.
Less common symptoms and signs include vision problems, eye
pain, redness of the white part of the eye, and a pupil (black part of
the eye) that does not get smaller when exposed to bright light.
History and Physical Exam
Your child’s doctor will likely ask about family members’
history of retinoblastoma or other cancers, and about the child's
symptoms. This information is important in deciding whether to have
additional tests and examinations by specialists. It is also useful in
determining whether other relatives could possibly pass this gene on to
their children or develop this cancer themselves (if they are younger
than 5 years old) and might benefit from genetic counseling.
If signs and symptoms suggest your child may have trouble
with his or her eye(s) that may be caused by a retinoblastoma, an ophthalmologist
(a doctor who specializes in diagnosis, surgery, and other treatments
for eye diseases) will examine the eye to be more certain about the
diagnosis. The ophthalmologist will use special lights and magnifying
lenses to look at the retina. General anesthesia to put the child to
sleep is usually necessary so that the doctor can take a careful and
detailed look. If the diagnosis is retinoblastoma, more tests will be
done to find out how far it has spread within the eye and to other
parts of the body. Usually the final determination will be made by an
ophthalmologist that specializes in treating cancers of the eye. This
person should also be part of the team of doctors treating the cancer.
Imaging Procedures
These are tests that produce images of organs and tissues
inside the body. The tests themselves are painless, although some may
require injections into the arm. These procedures are especially useful
in distinguishing between retinoblastoma and other eye diseases. They
also help determine how large the cancer is and how far it has spread.
Ultrasound: Ultrasound, also known as
ultrasonography, uses sound waves to create images of tissues inside
the body, such as the inner parts of the eye. For this test, a small
ultrasound probe is placed on the surface of the eye. The probe
releases high frequency sound waves and detects the sound wave echoes
that bounce off tissues inside the eye. A computer then translates the
pattern of echoes into an image of the eye and nearby tissues.
Ultrasound is used when tumors in the eye are so large they
prevent doctors from seeing inside the whole eye. Ultrasound can "see
through" tissues.
Computed tomography: Commonly known as a
CT or CAT scan, this test uses a rotating x-ray beam to create a series
of pictures of the body from many angles. A computer combines the
information from all the pictures to produce a detailed cross-sectional
image.
To highlight details on the CT scan, a harmless dye called
contrast medium may be injected before the x-rays are taken. CT scans
can help determine the size of a retinoblastoma tumor and its extent of
spread within the eye and to tissues near the eye. Normally, either a
CT or an MRI scan (see below) is needed for this purpose, but usually
not both.
Many doctors do not use CT scans in children to look for eye
tumors because they think the radiation in the CT scan may increase the
child’s chances of developing another cancer. Instead they use MRI.
Magnetic resonance imaging (MRI): MRI
scans use radio waves and strong magnets instead of x-rays to create
images. Body tissues absorb energy from the radio waves. The energy is
then released in a pattern affected by the type of tissue and by
certain diseases. A computer translates the pattern of radio waves
given off by tissues into a very detailed cross-sectional image (a
"slice") of parts of the body.
Because no radiation is used, MRI is often recommended to
evaluate the size and pattern of spread of a retinoblastoma. Most
patients with retinoblastoma will have at least one MRI scan to
evaluate their tumor. This also may require sedating the child to keep
him or her still during the MRI scan, which can take up to 45 minutes.
Radionuclide bone scan: A bone scan helps
show whether the retinoblastoma has spread to the skull and other
bones. The patient receives an injection of radioactive material. The
injection itself is the only uncomfortable part of the entire scanning
procedure. The amount of radioactivity involved is low in comparison to
the much higher doses used in radiation therapy, and this low level of
radiation does not cause any side effects.
The radioactive substance is attracted to diseased bone
throughout the entire skeleton. Areas of diseased bone show up on the
bone scan image as dense, gray areas, called "hot spots." These areas
may suggest metastatic cancer is present, but infections, bone injury,
or other bone diseases could also cause the same pattern. To
distinguish among these conditions, doctors may use other imaging tests
or take bone biopsies.
Most patients with retinoblastoma do not need to have a bone
scan. It is normally used only when there is strong reason to think
retinoblastoma may have spread beyond the eye.
For more detailed information on imaging tests, see the
American Cancer Society document, "Imaging
(Radiology) Tests."
Other Tests
Biopsy: In most cancers, a biopsy is
needed before the diagnosis can be made. Because trying to biopsy a
tumor at the back of the eye can damage the eye and spread the tumor,
this is never done to diagnose retinoblastoma. Instead, doctors rely on
its appearance when they are examining the eye with an ophthalmoscope,
usually while the patient is asleep.
Lumbar puncture (spinal tap):
Retinoblastomas may grow along the nerves that connect the eye to the
brain. Cancer that has spread to the surface of the brain can often be
detected by examining samples of cerebrospinal fluid, the fluid that
surrounds the brain and spinal cord.
A few milliliters (a teaspoon or less) of fluid are removed
through a thin needle placed between the vertebrae (backbones), near
the waistline. The fluid is examined under the microscope to check for
cancer cells.
Most patients with retinoblastoma do not need to have a
lumbar puncture. It is normally used only when there is strong reason
to think retinoblastoma may have spread into the brain.
Bone marrow aspiration and biopsy: Bone
marrow aspiration removes a few drops of bone marrow, the soft material
inside bones where blood cells are formed. During a bone marrow biopsy,
a small cylindrical piece of bone and bone marrow (about 1/16-inch in
diameter and ½-inch long) is removed. Both samples generally are taken
at the same time from the back of the hipbone, and doctors examine them
under a microscope to look for cancer cells.
These tests are used if retinoblastoma has spread to tissues
next to the eye and doctors suspect that the cancer may have also
spread through the bloodstream to the bone marrow.
Revised: 07/06/2006
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