How is retinoblastoma diagnosed?

Most types of cancer can be found by physical exam and imaging tests, but treatment is usually not begun until the diagnosis is confirmed by a biopsy. During a biopsy, the doctor removes a sample from the tumor and sends it to a lab to be looked at under a microscope.

But biopsies are not usually done to diagnose retinoblastoma for 2 reasons. First, taking a biopsy specimen from a tumor in the eye cannot be done easily without harming the eye and risking spreading the cancer cells outside of the eye. Second, retinoblastoma can be diagnosed accurately by doctors who have experience with this disease, and it is unlikely to be confused with other eye problems in children.

Signs and symptoms

Retinoblastomas are often found when a parent or doctor notices a child's eye looks unusual.

White pupillary reflex: This is the most common early sign of retinoblastoma. Normally when you shine a light in a child's eye, the pupil (the dark spot in the center of the eye) looks red because of the blood in vessels in the back of the eye. In an eye with retinoblastoma, the pupil often appears white or pink instead, which is known as a white pupillary reflex. This white glare of the eye may be noticed by a parent after a flash photograph is taken, especially if the pupils are different colors. It may also be noted by the child's doctor during a routine eye exam.

Lazy eye: Sometimes both eyes do not appear to look in the same direction, a condition often called lazy eye. (Doctors call this strabismus.) There are many possible causes of this in children. Most of the time lazy eye is caused by a mild weakness of the muscles that control the eyes, but retinoblastoma is also one of the rare causes.

Less common symptoms and signs of retinoblastoma include:

• Vision problems
• Eye pain
• Redness of the white part of the eye
• Bleeding in the front part of the eye
• Bulging of the eye
• A pupil that does not get smaller when exposed to bright light
• A different color in each iris (the colored part of the eye)

Medical history and physical exam

If your child has signs or symptoms that might be due to retinoblastoma, the doctor will want to examine your child's eyes and take a complete medical history. The doctor will probably ask about the family history of retinoblastoma or other cancers and about the child's symptoms. This information is important when deciding if more tests and exams by specialists are needed. Your family history is also useful for determining whether other relatives could possibly pass this gene on to their children or develop this cancer themselves (if they are young children) and might benefit from genetic counseling.

If a retinoblastoma is suspected, the doctor will refer you to an ophthalmologist (a doctor who specializes in eye diseases), who will examine the eye closely to be more certain about the diagnosis. The ophthalmologist will use special lights and magnifying lenses to look inside the eye. Usually, the child needs to be under general anesthesia (asleep) during the exam so that the doctor can take a careful and detailed look.

If a diagnosis of retinoblastoma seems likely, imaging tests will be done to help confirm it and to find out how far it may have spread within the eye and possibly to other parts of the body. Usually an ophthalmologist who specializes in treating cancers of the eye will make the final determination. This doctor should also be part of the team of doctors treating the cancer.

Imaging tests

Imaging tests use x-rays, sound waves, magnetic fields, or radioactive substances to create pictures of the inside of the body. The tests themselves are painless, but some may require injections. Imaging tests may be done for a number of reasons, including:

• To help distinguish between retinoblastoma and other eye diseases
• To determine how large the cancer is and how far it has spread
• To help determine if treatment has been effective

Children with retinoblastoma may have one or more of these tests.

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 sound waves and detects the echoes that bounce off the tissues inside and around the eye. The echoes are converted by a computer into a black and white image of the eye and nearby tissues that is displayed on a computer screen.

Ultrasound is one of the most commonly used imaging tests to confirm the diagnosis of retinoblastoma. It is painless and does not expose the child to radiation, but the child may need to be sedated (made sleepy) so that the doctor can get a good look at the eye. This test can be very useful when tumors in the eye are so large they prevent doctors from seeing inside the whole eye because ultrasound can “see through” tissues.

Computed tomography (CT) scan

The CT scan is an x-ray test that produces detailed cross-sectional images of parts of the body. Instead of taking one picture, like a regular x-ray, a CT scanner takes many pictures as it rotates around your child while he or she lies on a table. A computer then combines these pictures into images of slices of the part of the body being studied. Unlike a regular x-ray, a CT scan creates detailed images of the soft tissues in the body, such as the eye and surrounding structures.

Before the scan, your child may receive an IV (intravenous) injection of a contrast dye that helps better outline structures in the body. The dye may cause some flushing (a feeling of warmth, especially in the face). Some people are allergic and get hives. Rarely, more serious reactions like trouble breathing or low blood pressure can occur. Be sure to tell the doctor if your child has any allergies or has ever had a reaction to any contrast material used for x-rays.

CT scans take longer than regular x-rays, but not as long as MRI scans. Your child will need to lie still on a table while they are being done. During the test, the table slides in and out of the scanner, a ring-shaped machine that completely surrounds the table. Your child may need to be sedated before the test to stay still and help make sure the pictures come out well. Many medical centers now use spiral CT (also known as helical CT), which completes the scan more quickly. It also gives more detailed pictures and uses lower doses of radiation during the test.

CT scans can help determine the size of a retinoblastoma tumor and how much it has spread within the eye and to tissues near the eye. Normally, either a CT or an MRI scan (see the next section) is needed to do this, but usually not both. Because CT scans give off radiation, which might raise a child’s risk for other cancers in the future, most doctors now prefer to use MRI.

Magnetic resonance imaging (MRI) scan

Like CT scans, MRI scans provide detailed images of soft tissues in the body, such as the eye and surrounding structures. But MRI scans use radio waves and strong magnets instead of x-rays, so there is no radiation involved. The energy from the radio waves is absorbed by the body and then released in a pattern formed by the type of body tissue and by certain diseases. A computer translates the pattern into a very detailed image of parts of the body. A contrast material called gadolinium may be injected into a vein before the scan to better see details.

MRI scans may take up to an hour. Your child may have to lie inside a narrow tube, which is confining and can be upsetting. Newer, more open MRI machines can help with this, but the test still requires staying still for long periods of time. The machines also make buzzing and clicking noises that may be disturbing. Young children may be given medicine to help keep them calm or even asleep during the test.

MRI is often used to evaluate retinoblastomas because it provides very detailed images and does not use radiation. This test is especially good at looking at the brain and spinal cord. Most children with retinoblastoma will have at least one MRI scan to assess their tumor. For children with bilateral retinoblastomas, many doctors continue to do MRI scans of the brain for several years after treatment to screen for tumors of the pineal gland (sometimes called trilateral retinoblastoma).

Bone scan

A bone scan can help show if the retinoblastoma has spread to the skull and other bones. Most children with retinoblastoma do not need to have a bone scan. It is normally used only when there is a strong reason to think retinoblastoma may have spread beyond the eye.

For this test, a small amount of low-level radioactive material is injected into a vein (intravenously, or IV). The material settles in areas of damaged bone throughout the entire skeleton over the course of a couple of hours. Your child then lies on a table for about 30 minutes while a special camera detects the radioactivity and creates a picture of the skeleton. This may require sedation.

This test shows the entire skeleton at once. Areas of active bone changes appear as “hot spots” on the skeleton – that is, they attract the radioactivity. These areas may suggest the presence of cancer, but other bone diseases can also cause the same pattern. To help tell these conditions apart, other imaging tests such as plain x-rays or MRI scans, or even a bone biopsy might be needed.

For more detailed information on imaging tests, see our document called Imaging (Radiology) Tests.

Other tests

Some other types of tests are not commonly needed for retinoblastomas, but they may be helpful in some situations.

Biopsy

For most cancers, a biopsy (removing a tissue sample from the tumor and looking at it under a microscope) is needed to make a diagnosis. Trying to biopsy a tumor at the back of the eye can often damage the eye and may spread tumor cells, so this is almost never done to diagnose retinoblastoma. Instead, doctors make the diagnosis based on eye exams and on imaging tests such as those listed above. This is why it is very important that the diagnosis of retinoblastoma is made by experts.

Lumbar puncture (spinal tap)

Retinoblastomas may grow along the optic nerve, which connects the eye to the brain. If the cancer has spread to the surface of the brain, cancer cells can often be found in samples of cerebrospinal fluid (the fluid that surrounds the brain and spinal cord). Most children with retinoblastoma do not need to have a lumbar puncture. It is normally used only when there is a reason to think retinoblastoma may have spread into the brain.

For this test, the doctor first numbs an area in the lower part of the back over the spine. The child is typically given something so they will sleep and not move during the procedure. This can help ensure the spinal tap is done cleanly. A small, hollow needle is then placed between the bones of the spine to withdraw a small amount of the fluid. The fluid is then looked at under a microscope to check for cancer cells.

Bone marrow aspiration and biopsy

These 2 tests may be done to see if the cancer has spread to the bone marrow, the soft, inner part of certain bones. These tests are usually not needed unless the 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.

The tests are typically done at the same time. The samples are usually taken from the back of the pelvic (hip) bone, but in some cases they may be taken from the sternum (breastbone) or other bones.

In bone marrow aspiration, the skin over the hip and the surface of the bone may be numbed with a local anesthetic. This test can be painful, so the child will probably be given other medicines to reduce pain or even be asleep during the procedure. A thin, hollow needle is then inserted into the bone, and a syringe is used to suck out (aspirate) a small amount of liquid bone marrow.

A bone marrow biopsy is usually done just after the aspiration. A small piece of bone and marrow is removed with a slightly larger needle that is twisted as it is pushed down into the bone. Once the biopsy is done, pressure is applied to the site to help stop any bleeding.

The samples are then looked at under a microscope to see if tumor cells are present.