Diagnosis of retinoblastoma

Diagnosis is the process of finding out the cause of a health problem. Diagnosing cancer often means first ruling out other health conditions that share similar symptoms with cancer. It can be a very worrying time for you, your child and your loved ones. Sometimes this process is quick. Sometimes it can feel long and frustrating. But it’s important for doctors to get all the information they need before making a diagnosis of cancer.

Diagnosing retinoblastoma usually begins with a visit to your child’s doctor. The doctor will ask about any symptoms your child has and do a physical exam. Based on this information, the doctor may refer your child to a specialist or order tests to check for retinoblastoma or other health problems.

The following tests are usually used to diagnose or rule out retinoblastoma. Many of the same tests used to diagnose cancer are used to find out the stage (how far the cancer has spread). The doctor may also order other tests to check general health and to help plan treatment.

Your childʼs health history is a record of the symptoms and risks and all the medical events and problems that they have had in the past. The doctor will ask questions about your childʼs health history, including a family history of retinoblastoma.

A physical exam allows the doctor to look for any signs of retinoblastoma. During a physical exam, the doctor may:

• examine the eye for any signs of retinoblastoma
• feel the lymph nodes in the head and neck

Find out more about physical exams.

An eye exam is done by a doctor that specializes in eye care (called an eye doctor or ophthalmologist). Your child may see an eye doctor who specializes in eye diseases and vision care in children (called a pediatric ophthalmologist).

During an eye exam, the eye doctor will check your child’s vision and eye health and look for any signs of retinoblastoma. They will use eye drops to enlarge (dilate) your child’s pupils. This will help the doctor to see the structures inside the eye better.

Young children are often given general anesthesia (they will be asleep) before an eye exam to look for retinoblastoma. This type of eye exam may be called an EUA (examination under anesthesia). During an EUA, pictures can be taken of the inside of the eye to look at the size, shape and location of any tumours.

A doctor may examine an eye with different tools, including:

• ophthalmoscope – a lighted instrument with a magnifying lens that examines the back of the eye, including the retina and optic nerve
• slit lamp – a type of microscope that uses a strong beam of light to look at the inside of the eye

They may also perform different tests during the exam, including:

• retinal imaging – a digital scanning system that makes pictures of most of the retina
• optical coherence tomography (OCT) – uses light waves to take cross-sectional pictures of the retina, choroid and sclera
• fluorescein angiography – looks at the blood vessels and blood flow inside the eye

An eye exam is one of the main ways to diagnose retinoblastoma. Unlike other cancers, a biopsy is not used to diagnose retinoblastoma because it may increase the risk of the cancer spreading and damaging the eye.

An ultrasound uses high-frequency sound waves to make images of parts of the body. It is one of the most common tests to diagnose retinoblastoma.

The 2 types of ultrasounds used to diagnose retinoblastoma are B-scan ultrasound and ultrasound biomicroscopy (UBM).

An ultrasound is used to:

• take images of the eye and eye socket
• check for any calcification in the eye
• see how close the tumour is to important structures of the eye, such as the optic nerve
• see inside the whole eye, when large tumours prevent doctors from doing a complete eye exam

An eye ultrasound uses a small, wand-like instrument called an ultrasound probe. Itʼs gently placed over closed eyelids or directly on the eyeball. Special eye drops may be used to numb the eye before the ultrasound is done.

Find out more about ultrasounds.

RB1 stands for retinoblastoma 1. An RB1 gene test checks a sample of blood or tissue for any changes (mutations) in the RB1 gene. Mutations in the RB1 gene are often connected to retinoblastoma. Testing may be done at the hospital or cancer treatment centre.

An RB1 gene test can be done to help diagnose retinoblastoma, along with genetic counselling to help you understand the test results and treatment options.

Find out more about genetic testing.

Magnetic resonance imaging (MRI) uses powerful magnetic forces and radiofrequency waves to make cross-sectional images of organs, tissues, bones and blood vessels. A computer turns the images into 3D pictures.

An MRI is used to look at the size, number and location of tumours in the eye. An MRI can also be used to look for bleeding in the eye or a detached retina. It can also be used to see if cancer has spread to the brain or the eye socket around the eye.

For children with tumours in both eyes (called bilateral retinoblastoma), an MRI of the brain may be done regularly for several years after treatment. This is done to look for tumours in the pineal gland (called trilateral retinoblastoma).

Find out more about MRIs.

A computed tomography (CT) scan uses special x-ray equipment to make 3D and cross-sectional images of organs, tissues, bones and blood vessels inside the body. A computer turns the images into detailed pictures.

To diagnose retinoblastoma, an MRI is usually used instead of a CT scan because CT scans give off radiation that can increase a child’s risk of cancer in the future. But if a diagnosis of retinoblastoma is not clear from other tests, a CT scan may be used because it shows calcification and bones better than an MRI.

Find out more about CT scans.

A lumbar puncture removes a small amount of cerebrospinal fluid (CSF) from the spine. CSF surrounds and helps protect the brain and spinal cord. The fluid removed during a lumbar puncture is examined under a microscope to see if cancer has spread to the central nervous system (CNS).

A lumbar puncture is only done if retinoblastoma has grown along the optic nerve and may have spread to the surface of the brain.

A lumbar puncture may also be called a spinal tap.

Find out more about lumbar punctures.

A bone marrow aspiration and biopsy removes tissues or cells from the bone marrow. Itʼs not done very often, but may be done to see if cancer has spread to the bone marrow.

Find out more about a bone marrow aspiration and biopsy.

Children react to having these tests in different ways. Preparing your child for tests can help. Find more information on helping your child cope with tests and treatments.

To make the decisions that are right for your child, ask the healthcare team questions about diagnosis.