Diagnosis of retinoblastoma

Diagnosis is the process of finding out the cause of a health problem. Diagnosing retinoblastoma usually begins with a visit to your child’s doctor. The doctor will ask you 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 process of diagnosis may seem long and frustrating. It’s normal to worry, but try to remember that other health conditions can cause similar symptoms as retinoblastoma. It’s important for the healthcare team to rule out other reasons for a health problem before making a diagnosis of retinoblastoma.

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

A health history is a record of the symptoms, the risk factors and all the medical events and problems your child has had in the past. The doctor will ask questions about your child’s history of symptoms that suggest retinoblastoma.

Your child’s doctor may also ask about 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 an eye specialist (ophthalmologist). Your child may see an eye doctor who specializes in eye diseases and vision care in children (a pediatric ophthalmologist). During an eye exam, the doctor will check your child’s vision and eye health and look for any signs of retinoblastoma. Young children are often given general anesthesia (they will be unconscious) before an eye exam to look for retinoblastoma. This type of eye exam may be called an EUA (examination under anesthesia). During an EUA, photographic images of the inside of the eye can be made to map out the size, shape and location of any tumours.

Before an eye exam, the eye doctor uses eye drops to enlarge (dilate) the pupils. This helps the doctor to see the structures inside the eye better.

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

An ultrasound uses high-frequency sound waves to make images of parts of the body. An ultrasound of the eye and eye socket (orbit) may be done under anesthesia depending on the child’s age. It can help to find any calcification and to see how close the tumour is to important structures of the eye, such as the choroid and sclera. An eye ultrasound uses a small, wand-like instrument called an ultrasound probe. It is gently placed over closed eyelids or directly on the surface of the eye. Anesthetic eye drops are sometimes used to numb the eye before the ultrasound is done.

Find out more about ultrasounds.

RB1 stands for retinoblastoma 1. An RB1 gene test is a lab test that involves testing a sample of blood or tissue to see if there are any changes (mutations) in the RB1 gene. Mutations in the RB1 gene are often connected to retinoblastoma. When the test is done will depend on whether the testing will be done at your child’s treatment centre or at a referral centre, as well as specific features of your child’s tumour. Testing can be done at the time of diagnosis or at a later time, along with genetic counselling.

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 and number of tumours and to see whether a tumour involves certain structures of the eye, such as the optic nerve. An MRI can also be used to look for bleeding in the eye or a detached retina. It can be used to see if the cancer has spread to the brain or spinal cord.

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

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 calcium deposits and bones better than an MRI.

Find out more about CT scans.

A bone scan uses bone-seeking radioactive materials called radiopharmaceuticals and a computer to create a picture of the bones. It is used to see if cancer has spread to the skull or other bones.

Find out more about bone scans.

During bone marrow aspiration and biopsy, the doctor removes tissues or cells from the bone marrow to be tested in a lab. Bone marrow aspiration and biopsy are not done very often but may be done to see if cancer has spread to the bone marrow.

Find out more about bone marrow aspiration and biopsy.

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