How Is Retinoblastoma Diagnosed?

Retinoblastomas are usually found when a child is brought to a doctor because he or she has certain signs or symptoms.

For most types of cancer, the diagnosis is made with 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 can’t be done easily without harming the eye and risking spreading cancer cells outside the eye. Second, retinoblastoma can usually be diagnosed accurately without a biopsy by doctors who have experience with this disease, and it’s unlikely to be confused with other eye problems in children.

Medical history and physical exam

If your child has signs or symptoms of retinoblastoma, the doctor will examine your child’s eyes and get a complete medical history. The doctor will ask about the child’s symptoms and may ask about any family history of retinoblastoma or other cancers. This information is important when deciding if more tests and exams are needed. Your family history is also useful for determining whether other relatives could possibly pass the retinoblastoma (RB1) gene change 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 based on the eye exam, 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 (called an ocular oncologist) 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. Imaging tests may be done for a number of reasons, including:

  • To help tell if a tumor in the eye is likely to be a retinoblastoma
  • To determine how large the tumor is and how far it has spread
  • To help determine if treatment is working

Children thought to have retinoblastoma may have one or more of these tests.


Ultrasound 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 up against the eyelid or eyeball. The probe gives off sound waves and detects the echoes that bounce off the tissues inside and around the eye. The echoes are converted by a computer into an image on a computer screen.

Ultrasound is one of the most common imaging tests for confirming the diagnosis of retinoblastoma. It is painless and does not expose the child to radiation, but the child may need to be given medicine to help keep them calm or even asleep so 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.

Optical coherence tomography (OCT) is a similar type of test that uses light waves instead of sound waves to create very detailed images of the back of the eye.

Magnetic resonance imaging (MRI) scan

MRI scans are often used for retinoblastomas because they provide very detailed images of the eye and surrounding structures without using 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. For children with bilateral retinoblastomas (tumors in both eyes), many doctors continue to do MRI scans of the brain for several years after treatment to look for tumors of the pineal gland (sometimes called trilateral retinoblastoma).

Unlike CT scans (described next), MRI scans use radio waves and strong magnets to create images instead of x-rays. A contrast material called gadolinium may be injected into a vein before the scan to show details better.

MRI scans can 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.

Computed tomography (CT) scan

CT scans use x-rays to make detailed images of parts of the body. CT scans can help determine the size of a retinoblastoma tumor and how much it has spread within the eye and to nearby areas.

Normally, either a CT or an MRI scan is needed, 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 prefer to use MRI. However, a CT scan can show deposits of calcium in the tumor much better than an MRI, which can be very helpful when the diagnosis of retinoblastoma is not clear.

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.

Before the scan, your child may get an IV (intravenous) injection of a contrast dye that helps better outline structures in the body. The dye can 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 (especially to iodine or shellfish) 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. A CT scanner has been described as a large donut, with a narrow table that slides in and out of the middle opening. Your child will need to lie still on the table while the scan is being done. Your child may be given medicine to help them stay calm or even go to sleep during the test to help make sure the pictures come out well.

Bone scan

A bone scan can help show if the retinoblastoma has spread to the skull or other bones. Most children with retinoblastoma don’t need to have a bone scan. It is normally used only when there is a strong reason to think retinoblastoma might 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 amount of radioactivity used is very low and will pass out of the body within a day or so.) The material settles in abnormal areas of bone throughout the body 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. Younger children may be given medicine to help them stay calm or even go to sleep during the test.

Areas of active bone changes appear as “hot spots” on the scan. These areas may suggest cancer is in an area, but other bone diseases can also cause the same pattern. To help tell these apart, other tests such as plain x-rays or MRI scans of the bone might be needed.

For more details on imaging tests, see Imaging (Radiology) Tests.

Other tests

Other tests are not often needed for retinoblastomas, but they may be helpful in some situations.


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 can sometimes grow along the optic nerve, which connects the eye to the brain. If the cancer has spread to the surface of the brain, this test can often find cancer cells in samples of cerebrospinal fluid (the fluid that surrounds the brain and spinal cord). Most children with retinoblastoma don’t need to have a lumbar puncture. It is used mainly when there is a reason to think retinoblastoma might have spread into the brain.

For this test, the child is typically given anesthesia so they will be asleep and not move during the procedure. This can help ensure the spinal tap is done cleanly. The doctor first numbs an area in the lower part of the back over the spine. 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 grown outside 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 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 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 they contain cancer cells.

The American Cancer Society medical and editorial content team
Our team is made up of doctors and master's-prepared nurses with deep knowledge of cancer care as well as journalists, editors, and translators with extensive experience in medical writing.

Last Medical Review: March 12, 2015 Last Revised: March 12, 2015

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