8 Commonly Confused Retinoblastoma Terms, What They Mean and Why Getting Them Right Matters.


Sunday November 25, 2018


Do you know the difference between a lazy eye and a squint, or an Ocular Oncologist and a Paediatric Oncologist?  Do you know when extraocular retinoblastoma becomes metastatic, or why trilateral retinoblastoma is neither of these?   WE C Hope CEO Abby White explains these and other terms, and why using them correctly is important.


Navigating life with retinoblastoma can be a very confusing experience. Even before diagnosis, families rapidly amass information from medical professionals, support organizations, other parents and survivors, general awareness, and Doctor Google.  The process reveals a bewildering slew of terms whose meanings or connection with other terms may be unclear.

Below, we define eight commonly confused sets of terms, and discuss why confusion is harmful and getting them right is important.

This is Part 1 in a mini-series. Read Part 2: 10 Commonly Confused Terms.

A baby has a squint - the right eye is rutned in towards the nose.

This baby has esotropia, a type of squint in which one or both eyes turns in towards the nose.

1. Lazy Eye and Squint

Lazy Eye: medically termed amblyopia – usually affecting one eye, the eye doesn’t develop properly and vision is below normal, even with prescription glasses or contact lenses.

Squint: medically termed strabismus – the eyes are misaligned, either inward (esotropia), outward (exotropia), upward (hypertropia) or downward (hypotropia). Strabismus can be constant or intermittent.

Why This Matters

Lazy eye is not a sign of retinoblastoma, but parents often incorrectly refer to squint as “lazy eye” when describing what alerted them to their child’s eye cancer.  Squint is a common sign of retinoblastoma, often incorrectly dismissed by primary health professionals as a condition that will resolve naturally with age.  Using the correct term is vital to raise awareness of squint as an early sign of retinoblastoma, and to avoid confusion that can delay diagnosis.

2. Ocular Oncologist and Paediatric Oncologist

Ocular Oncologist: An ophthalmologist (eye doctor) who specialises in treating cancers of the eye.  After training in ophthalmology, they have completed a further fellowship in cancers of the eye.  They may have taken an additional fellowship in the treatment of retinoblastoma.  The doctor may or may not be a paediatric ophthalmologist – an eye doctor who has completed a further fellowship in the treatment of children’s eye conditions.

Paediatric Oncologist: A children’s doctor who specialises in the treatment of cancer.  After training in paediatrics, they have taken additional fellowships in the treatment of childhood cancer. This may or may not include specialism in the treatment of retinoblastoma.

Why This Matters

Children with retinoblastoma should be treated by an experienced ophthalmologist and oncologist who work together to plan and deliver care.  They bring together different areas of expertise that are vital to retinoblastoma care.

The paediatric oncologist may or may not have specific knowledge of retinoblastoma management, and cannot independently treat the cancer with the goal of saving sight.  The ocular oncologist may or may not have experience of managing the whole-body and psychological effects of cancer, can rarely deliver eye-salvage therapy without paediatric oncology collaboration, and cannot independently treat cancer that has spread beyond the eye.

When cancer is contained in the eye, the ophthalmologist leads the medical team. When cancer has spread outside the eye, the oncologist will lead the team. But the two disciplines should always work together for the best outcome.

3. Unilateral and Bilateral Retinoblastoma

Unilateral: One or more tumours affecting only one eye.

Bilateral: One or more tumours affecting both eyes.

Why This Matters

Retinoblastoma does not spread from one eye to the other.  Individual tumours arise from unique retinal cells in each eye as genetic mutations occur in that individual retinal cell.  Multiple tumours in both eyes are common in children with a heritable RB1 mutation.  The presence of retinoblastoma in one eye does not affect the process of genetic mutations within other retinal cells in the same eye or the other eye.

A baby has one red pupil and one white pupul - the classic early sign of eye cancer in children.

Leukocoria – white pupil – is the most common reported early sign of cancer in both unilateral and bilateral Rb.

4. New Tumour, Seeds and Relapse

New Tumour: Tumours that form in the eye after the initial diagnosis of retinoblastoma.  New tumours can arise at any time while the eye continues to develop.  The risk reduces with age, and usually disappears completely by age 5-6.

Seeds: fragments of cancerous cells that break off the main tumour, float into the fluid between the retina and the choroid (subretinal seeds) or the fluid-filled centre of the eye (vitreous seeds), and begin to grow independently.

Relapse: Cancer that becomes active again after a period of remission.  A relapse may occur within the eye after eye salvage therapy, or outside the eye after eye salvage therapy or enucleation.  The risk of relapse may continue for several years beyond active treatment, depending on the child’s diagnosis and treatment history.  Doctors sometimes describe relapsed tumour as “new tumour growth”.

Why This Matters

New tumours are very common in children with a heritable RB1 mutation, but do not occur in children with non-heritable retinoblastoma.

Having more than one tumour in one eye strongly indicates the child’s risk for a heritable RB1 mutation, but differentiating between true tumour and a large seed that look like a unique tumour can be very difficult.

If a child with unilateral retinoblastoma is diagnosed with “new tumour growth” during or after eye salvage therapy, it is important parents ask questions to clarify the situation.  Does the child have a new tumour that was not previously detected, seeds that look like new tumours, or new growth (relapse) of the previously treated tumour?  Knowing the answer will help identify other questions to ask for the child’s best care.

A baby born with retinoblastoma may have successful treatment in the first months of life, and experience no relapse.  This is very positive, but their risk of new tumours continues.  Another child may have multiple relapses of one or more previously treated tumours, over several months or years.   Yet another child may experience a combination of new tumours and relapse of previously treated tumours over months or years.  When friends and relatives understand this situation, compassionate support for the family continues beyond active treatment, through the years of surveillance care.

5. Extraocular, Metastatic and Trilateral Retinoblastoma

Extraocular Retinoblastoma: Cancer that has spread anywhere outside the eye, e.g. the orbital tissues, lymph nodes, optic nerve, and beyond.

Metastatic Retinoblastoma: Cancer that has spread to distant sites beyond the eye e.g. the brain, bone marrow or other parts of the body.

Trilateral Retinoblastoma: A rare type of primary retinoblastoma arising in the pineal gland, suprasellar or parasellar region of the brain.  TRb affects only children with a heritable RB1 mutation, and brain cells that are similar to retinal cells.

Why This Matters

Trilateral retinoblastoma is entirely independent of cancer within the eye – it does not spread from the eye and is thus completely different from metastatic retinoblastoma.  Primary trilateral retinoblastoma may itself become metastatic if it spreads to other distant parts of the brain or spine or other parts of the body.

When retinoblastoma spreads from the eye, cancer cells in the new location are cancerous retinal cells.  When trilateral retinoblastoma develops, the cancer is formed of cancerous brain cells.   For this reason, different treatments may be more or less effective for cancer that has spread from the eye and trilateral retinoblastoma.

When a child with retinoblastoma develops cancer in the brain after initial treatment of their eye cancer, correct diagnosis has important implications for care beyond direct treatment of the brain cancer.

If the child was previously diagnosed with unilateral retinoblastoma, a diagnosis of trilateral retinoblastoma will also imply a heritable RB1 mutation that may previously have been unknown. Genetic testing will be important to confirm this and identify any blood relatives at risk of developing retinoblastoma.

If the child received eye salvage therapy, correctly diagnosing subsequent brain cancer is vital.  Both for the child and family’s welfare, and to record true figures of metastatic cancer after eye salvage.  This is particularly important when the child has a known or suspected heritable RB1 mutation, and thus a risk of trilateral retinoblastoma, as well as a potential risk for metastatic retinoblastoma.

Damian and his mother hug and share a smile, leaning against a tree. Damian is bald, wearing a spiderman t-shirt.

Damian’s cancer spread to his brain after eye salvage therapy.

6. Eye Transplant and Corneal Transplant

Eye Transplant: There is no such thing as a whole-eye transplant. The optic nerve, which connects the eye to the brain, cannot currently be regrown or transplanted.

Corneal Transplant: Surgical replacement of a diseased cornea with a cornea from a deceased donor.  The cornea is the clear covering that sits over the iris (coloured ring) and pupil (black circle) at the front of the eye and supports healthy vision.

Why This Matters

People often say they have heard of a miraculous “eye transplant” restoring sight. Families ask if it is possible to restore their child’s sight or cure their cancer with such a transplant.  Parents resist vital life-saving eye removal surgery, believing they will destroy their child’s chance of a vision-restoring transplant if the eye is removed – and potentially curable children die as a result of these delays.  Some parents regret their swift consent after the surgery, believing they were lied to about availability of the “eye transplant”.

The emotional toll is significant, and based entirely on myth and misinformation.

Corneal transplant is often incorrectly referred to as an “eye transplant” by patients, the general public, journalists, and even some doctors, causing this dangerous confusion and false hope.  This is currently the only available surgery transplanting eye tissue.  Corneal transplant may be beneficial for people cured of retinoblastoma who have corneal damage resulting from treatment, e.g., corneal vascularisation arising from radiotherapy.  But it cannot aid the management or cure of retinoblastoma in any way.

Recommended eye removal surgery should never be delayed to investigate the possibility of an eye transplant.  This option does not exist, and is extremely unlikely to become a reality within the next few decades.  Surgery is only advised when life is already at risk, so delaying care further puts the child’s life in great danger.

7. Child life and Play Therapy

Child Life: Preparation, education, distraction and psychological supports using play, based on natural child development, designed to help the child cope with serious illness and other traumatic life events that are happening to them now.

Play Therapy: A form of counselling or psychotherapy in which play helps children express and manage strong feelings, share and work through difficult experiences, and cope with trauma that has happened in the distant or recent past.

Why This Matters

Both child life and play therapy harness a child’s natural ability for self-expression, discovery, learning and mastery through play.  Both help children safely explore their feelings, work through difficult experiences, improve communication, solve problems and learn healthy ways of coping. But their roles are quite different.

In retinoblastoma care, child life specialists work with babies and children who are currently undergoing medical care, or are expected to undergo medical procedures.  Their goal is to help prevent or reduce trauma from the experience, and improve the child’s quality of life.

In contrast, play therapists work with children already affected by trauma, and children who have other mental health concerns.  Their goal is to help children articulate and understand their experiences and feelings, manage their emotions, and improve their mental health.

An experienced play therapist can help a child work through the traumatic aftermath of retinoblastoma treatment.  But highly skilled child life specialists integrated into the ophthalmology and oncology clinics can prevent that trauma from ever developing.

Confusion arises because of the varying terms worldwide.  For example, in the UK, child life specialists are called “hospital play specialists”.  This term was also used in Australia until recently when it was changed to “child life therapist”.  As a result, some medical professionals incorrectly refer to child life specialists and play specialists as “play therapists”.

Practicing medical procedures helps children gain mastery and diffuse fear.

8. Secondary Cancer and Second Primary Cancer

Secondary Cancer: Another term for metastatic cancer – cancer that has spread from the original site to another part of the body.

Second Primary Cancer: A second (or subsequent) cancer that is not directly related to the original cancer, arising in a different organ or tissue.

Why This Matters

The terms secondary cancer and second primary cancer are often used interchangeably, but they mean very different things.

Secondary retinoblastoma has spread from the eye to the brain, bone marrow or other distant sites.  The cancer at the secondary site is made up of cancerous retinal cells that have travelled from the eye to that location.  Second primary cancers arise directly from the cells of the bone, skin, soft tissue, brain or other tissue or organ affected – they are not a metastasis of the original retinoblastoma.

Secondary retinoblastoma can potentially occur in any child with retinoblastoma.  Any child who is diagnosed late or not at all, whose treatment is delayed, or who is treated inappropriately.  Risk of secondary retinoblastoma can be reduced or eliminated entirely by diagnosing children early and ensuring appropriate treatment and follow up care for every stage of cancer.

There is no increased risk of second primary cancer for a child with non-heritable retinoblastoma who did not receive chemotherapy or radiotherapy.

Second primary cancer risk is high in carriers of a heritable RB1 mutation, and elevated in children treated with chemotherapy or radiotherapy.  Risk can be reduced by avoiding over-treatment with chemotherapy and radiotherapy, but it remains high in carriers of an RB1 mutation.  Lifelong follow-up care, regular imaging, and investigation of unexplained symptoms are vital for this group of survivors.

Understanding the difference between secondary and second primary cancers can help parents and survivors explain and clarify risk.  Especially when conveying information to primary doctors and other medical professionals who may not be familiar with retinoblastoma and lifelong risks.

About the Author

Abby’s father was diagnosed with bilateral retinoblastoma in Kenya in 1946. Abby was also born with cancer in both eyes. She has an artificial eye and limited vision in her left eye that is now failing due to late effects of radiotherapy in infancy.

Abby studied geography at university, with emphasis on development in sub-Saharan Africa. She co-founded WE C Hope with Brenda Gallie, responding to the needs of one child and the desire to help many in developing countries.  After receiving many requests for help from American families and adult survivors, she co-founded the US chapter to bring hope and encourage action across the country.

Abby enjoys listening to audio books, creative writing, open water swimming and long country walks.