Definition
Clinical picture
Retinoblastoma is a rare cancer of the eye.
It develops in the retina and occurs almost exclusively in children.
A distinction is made between a hereditary and a non-hereditary form of the disease.
In the first case, there is a predisposition for the development of this type of cancer, in the second case, the cancer develops spontaneously, i.e. as a result of a newly occurring change in a retinal cell.
Definition of
A retinoblastoma can affect one or both eyes.
In most cases (around 60% of cases), only one eye is affected, which is referred to as unilateral or unilateral retinoblastoma.
In around 40% of children, the disease affects both eyes (bilateral retinoblastoma).
If the latter is the case, this is almost always an indication of a hereditary retinoblastoma.
Unilateral retinoblastomas, on the other hand, are usually not hereditary.
The tumors can either form at only one location in the eye (unifocal) or at several locations (multifocal).
Retinoblastomas usually grow rapidly.
They can spread within the eyeball and, starting from there, also into the eye socket and along the optic nerve into the central nervous system (CNS), and in advanced cases also into other organs via the blood and/or lymphatic system.
If the disease remains untreated, it is almost always fatal.
Only in very rare cases (1%) does the tumor regress on its own; this is referred to as spontaneous regression.
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More Information
Frequency
Retinoblastoma is the most common malignant tumor occurring in the eye (intraocular) in children.
According to the German Childhood Cancer Registry (Mainz), around 45 children under the age of 18 are newly diagnosed with this form of cancer in Germany every year.
Overall, however, retinoblastomas are rare: They account for around 2% of all malignant diseases in children and adolescents.
Retinoblastoma usually occurs in infants and young children, i.e. almost all affected children are under 5 years old, although bilaterally affected children are usually younger than those with unilateral retinoblastoma.
The average age of onset is 1 year.
Boys are affected slightly more frequently than girls (gender ratio: 1.1:1).
Causes
The development of retinoblastoma is caused by two genetic changes (mutations) in the precursor cells of the retina. Such changes can occur spontaneously in individual retinal cells.
However, they can also be present in the germ cells (and therefore also in all body cells) and are then hereditary.
Just over half of the patients have a non-hereditary form of retinoblastoma, i.e. the mutations have arisen in isolation (sporadically) and are located exclusively in the tumor cells. However, almost 50% of retinoblastomas are hereditary. In around a quarter of these cases – i.e. in a total of 10 to 15% of all patients – other diseases are already known in the family (this is also referred to as familial retinoblastoma).
Regardless of whether it is a hereditary or non-hereditary retinoblastoma, the genetic changes are always located in the so-called retinoblastoma gene, which is found on chromosome 13.
As each chromosome is present in duplicate, there are also two retinoblastoma gene alleles in each cell.
A tumor can only develop if both alleles are altered.
However, as all retinal cells in hereditary retinoblastoma already have an altered retinoblastoma gene allele from the outset, “only” one further mutation is necessary for tumor development.
Therefore, the hereditary form usually occurs at a very early age, in both eyes (bilateral) and often at several sites (multifocal) within one eye. For children who have inherited the diseased gene, the risk of developing retinoblastoma is almost 100%.
As the predisposition to other cancers is also increased, hereditary retinoblastoma is also referred to as cancer predisposition syndrome.
Signs of illness
Very small retinoblastomas usually do not cause any symptoms; the disease often progresses for a long time without any signs of illness (symptoms).
Symptoms usually only occur when the tumor is larger or grows into other parts of the eye.
This can lead to impaired vision or even blindness.
However, the most common initial symptom in over two thirds of children with the disease is a white pupil (leukocoria) that lights up in certain light conditions, for example when taking photographs – in contrast to a red pupil or a black pupil in a healthy eye.
This white pupil, also known as a cat’s eye, can be an indication of tumor growth in the eye.
In addition, strabismus can occur in the affected eye due to the misalignment of the visual axis.
More rarely, children are affected by other visual disorders or by a painful, reddened and/or swollen eye due to increased intraocular pressure.
However, the occurrence of one or more of these symptoms does not necessarily mean that a retinoblastoma or other tumor disease is present. Some of these symptoms can also have comparatively harmless causes that have nothing to do with a tumor.
Nevertheless, it is advisable to consult a doctor as soon as possible to clarify the cause.
If a retinoblastoma (or another malignant disease) is actually present, a timely diagnosis is the best prerequisite for successful treatment of the disease.
Sources: Maria Yiallouros, editorial team kinderkrebsinfo.de
What is leukocoria?
Leukocoria means ‘white pupil’ and occurs when the typical red pupillary reflex is absent, e.g. in photographs.
Causes can be retinoblastoma, cataracts, retinopathy of prematurity, retinal or choroidal coloboma and rare hereditary diseases.
Immediate clarification by an ophthalmologist is required.
Good to know
Children from families with a hereditary increased risk of retinoblastoma should receive regular ophthalmologic examinations, even without any recognizable complaints or symptoms.
This enables early detection of the disease and the timely initiation of appropriate treatment measures.
Worldwide, around 1:20,000 children fall ill every year, regardless of their origin or gender.
If detected early, 95% of children are cured in medically well-developed countries.
In developing countries, up to 80% of children die because they are diagnosed too late.
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