Most suspected cancers of children and adults can be found by physical exam and imaging tests. But treatment is usually not begun until the diagnosis is confirmed by a biopsy (removing a tissue sample from the tumor and looking at it under a microscope).

But biopsies are not usually needed to diagnose retinoblastoma 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 done easily without harming the eye and risking spreading the cancer cells outside of the eye.

Signs and symptoms

Retinoblastomas are usually found because a parent or pediatrician notices a child's eye looks unusual.

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. This white glare of the eye may be noticed after a flash photograph is taken. This is often the earliest sign detected by most parents and the most common reason a doctor's help is sought.

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, and a pupil that does not get smaller when exposed to bright light.

History and physical exam

If your child has signs or symptoms that may suggest retinoblastoma, your child's doctor will want to take a complete medical history. The doctor will probably ask about family members' history of retinoblastoma or other cancers, and about the child's symptoms. This information is important in deciding if more tests and exams by specialists are needed. 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's eye trouble may be caused by a retinoblastoma, the doctor will probably refer you to an ophthalmologist (a doctor who specializes in diagnosis, surgery, and other treatments for eye diseases), who 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. 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 the diagnosis is retinoblastoma, imaging tests will be done to find out how far it may have spread within the eye and 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, although some may require injections. These tests are very useful in distinguishing between retinoblastoma and other eye diseases. They may also be used to 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 sound waves and detects the echoes that bounce off tissues inside 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 retinoblastoma is present. It is very useful when tumors in the eye are so large they prevent doctors from seeing inside the whole eye because ultraound can "see through" tissues.

Computed tomography scan

The computed tomography scan (better known as a CAT or 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.

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 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 moves in and out of the scanner, a ring-shaped machine that completely surrounds the table. Some people feel a bit confined by the ring they have to lie in while the pictures are being taken. In some cases, your child may need to be sedated before the test to keep them still and help make sure the pictures come out well.

In recent years, spiral CT (also known as helical CT) has become available in many medical centers. This type of CT scan uses a faster machine. The scanner part of the machine rotates around the body continuously, allowing doctors to collect the images much more quickly than with a standard CT. This lowers the chance of blurred images occurring as a result of breathing motion. It also lowers the dose of radiation received during the test. The biggest advantage may be that the "sliced" images are thinner, and yield more detailed pictures that allow doctors to look at suspicious areas from different angles.

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 below) is needed to do this, but usually not both. Because CT scans give off radiation, some doctors prefer to use MRI.

Magnetic resonance imaging scan

Like CT scans, magnetic resonance imaging (MRI) scans provide detailed images of soft tissues in the body. 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.

The inside of most MRI machines is like a narrow tunnel. Your child has to lie inside, which can feel confining. Although newer "open" MRI machines can help with this feeling, the test still requires a person to stay still for long periods of time. It may take up to an hour to have an MRI scan. The machines also make buzzing and clicking noises that may be disturbing. This may require that the child is sedated before testing.

Because no radiation is used, MRI is often recommended to evaluate the size and pattern of spread of a retinoblastoma. This test is especially good at looking at the brain and spinal cord. Most patients with retinoblastoma will have at least one MRI scan to evaluate their tumor. For children with the bilateral form, many doctors continue to do MRI scans of the brain for 3 or 4 years, to screen for tumors of the pineal gland.

Bone scan

A bone scan helps show if the retinoblastoma has spread to the skull and other bones. This test is useful because it gives a picture of the entire skeleton at once.

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.

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 distinguish between these conditions, other imaging tests such as plain x-rays or MRI scans, or even a bone biopsy might be needed.

Most patients 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 more detailed information on imaging tests, see the American Cancer Society document, "Imaging (radiology) tests."

Other tests

Biopsy

For most cancers, a biopsy (removing a tissue sample from the tumor and looking at it under a microscope) is done to make a diagnosis. Because trying to biopsy a tumor at the back of the eye can often damage the eye and spread the tumor, this is almost never done to diagnose retinoblastoma. Instead, doctors make the diagnosis based on the eye exam and on imaging tests such as those listed above. In very rare cases where the diagnosis is still not clear, a very thin, hollow needle may be used to get a biopsy sample of tumor cells.

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 seen in samples of cerebrospinal fluid, (the fluid that surrounds the brain and spinal cord).

For this test, the doctor first numbs an area in the lower part of the back near the spine. The doctor may also recommend that the child be given something so they will sleep and not squirm during the procedure. Squirming may keep the spinal tap from being 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.

Most patients 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.

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. The tests are typically done at the same time. The samples are usually taken from the back of the pelvic (hip) bone, although 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 are numbed with a local anesthetic. This test can be painful, so the child will probably also 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 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 (about 1/16 inch in diameter and 1/2 inch long) is removed with a slightly larger needle that is twisted as it is pushed down into the bone. Once the biopsy is done, pressure will be applied to the site to help stop any bleeding.

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

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.