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.