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Retinoblastoma (Rb) is a rare form of
cancer Cancer is a group of diseases involving abnormal cell growth with the potential to invade or spread to other parts of the body. These contrast with benign tumors, which do not spread. Possible signs and symptoms include a lump, abnormal b ...
that rapidly develops from the immature cells of a
retina The retina (from la, rete "net") is the innermost, light-sensitive layer of tissue of the eye of most vertebrates and some molluscs. The optics of the eye create a focused two-dimensional image of the visual world on the retina, which the ...
, the light-detecting tissue of the eye. It is the most common primary malignant intraocular cancer in children, and it is almost exclusively found in young children. Though most children survive this cancer, they may lose their vision in the affected eye(s) or need to have the eye removed. Almost half of children with retinoblastoma have a hereditary
genetic defect A genetic disorder is a health problem caused by one or more abnormalities in the genome. It can be caused by a mutation in a single gene (monogenic) or multiple genes (polygenic) or by a chromosomal abnormality. Although polygenic disorde ...
associated with retinoblastoma. In other cases, it is caused by a
congenital A birth defect, also known as a congenital disorder, is an abnormal condition that is present at birth regardless of its cause. Birth defects may result in disabilities that may be physical, intellectual, or developmental. The disabilities can ...
mutation in the
chromosome 13 Chromosome 13 is one of the 23 pairs of chromosomes in humans. People normally have two copies of this chromosome. Chromosome 13 spans about 114 million base pairs (the building material of DNA) and represents between 3.5 and 4% of the total DNA ...
gene 13q14 ( retinoblastoma protein).


Signs and symptoms

Retinoblastoma is universally known as the most intrusive intraocular cancer among children. The chance of survival and preservation of the eye depends fully on the severity. Retinoblastoma is extremely rare as there are only about 200 to 300 cases every year in the United States. Looking at retinoblastoma globally, only 1 in about 15,000 children have this malignancy but these numbers continuously increase. Intraocular malignancies are more curable rather than extraocular malignancies due to early diagnosis and an early treatment prognosis. During infant screenings, if they incorporate an eye screening like they do a hearing screening, it can be detected at an earlier age, therefore, preventing its spread. Leucocoria is the primary indication of retinoblastoma and is when the cancer is still intraocular, meaning inside the eye. When light is reflected by the white tumor, the view of the red retina is blocked. Retinoblastoma can be curable after the initial sign and up to six months, if the tumor is intraocular. If you do not visit an ophthalmologist with signs of leucocoria within a reasonable amount of time, the delay in the diagnosis could lead to a more severe prognosis. Due to a delay in the diagnosis, it could result in proptosis which is then considered extraocular, the most severe. The most common and obvious
sign A sign is an object, quality, event, or entity whose presence or occurrence indicates the probable presence or occurrence of something else. A natural sign bears a causal relation to its object—for instance, thunder is a sign of storm, or ...
of retinoblastoma is an abnormal appearance of the retina as viewed through the pupil, the medical term for which is
leukocoria Leukocoria (also white pupillary reflex) is an abnormal white reflection from the retina of the eye. Leukocoria resembles eyeshine, but leukocoria can also occur in animals that lack eyeshine because their retina lacks a ''tapetum lucidum''. Leuk ...
, also known as amaurotic cat's eye reflex. Other signs and symptoms include deterioration of vision, a red and irritated eye with
glaucoma Glaucoma is a group of eye diseases that result in damage to the optic nerve (or retina) and cause vision loss. The most common type is open-angle (wide angle, chronic simple) glaucoma, in which the drainage angle for aqueous humor, fluid withi ...
, and faltering growth or delayed development. Some children with retinoblastoma can develop a squint, commonly referred to as "cross-eyed" or "wall-eyed" (
strabismus Strabismus is a vision disorder in which the eyes do not properly align with each other when looking at an object. The eye that is focused on an object can alternate. The condition may be present occasionally or constantly. If present during a ...
). Retinoblastoma presents with advanced disease in developing countries and eye enlargement is a common finding. Depending on the position of the tumors, they may be visible during a simple eye examination using an
ophthalmoscope Ophthalmoscopy, also called funduscopy, is a test that allows a health professional to see inside the fundus of the eye and other structures using an ophthalmoscope (or funduscope). It is done as part of an eye examination and may be done as part ...
to look through the
pupil The pupil is a black hole located in the center of the Iris (anatomy), iris of the Human eye, eye that allows light to strike the retina.Cassin, B. and Solomon, S. (1990) ''Dictionary of Eye Terminology''. Gainesville, Florida: Triad Publishing ...
. A positive diagnosis is usually made only with an examination under anesthetic ( EUA). A white eye reflection is not always a positive indication of retinoblastoma and can be caused by light being reflected badly or by other conditions such as
Coats' disease Coats' disease is a rare congenital, nonhereditary eye disorder, causing full or partial blindness, characterized by abnormal development of blood vessels behind the retina. Coats' disease can also fall under glaucoma. It can have a similar pr ...
. The presence of the photographic fault red eye in only one eye and not in the other may be a sign of retinoblastoma. A clearer sign is "white eye" or "cat's eye" (leukocoria).Introduction to White Eye
, Daisy's Eye Cancer Fund.


Cause

Mutation of genes, found in chromosomes, can affect the way in which cells grow and develop within the body. Alterations in RB1 or MYCN can give rise to retinoblastoma.


RB1

In children with the heritable genetic form of retinoblastoma, a mutation occurs in the '' RB1'' gene on
chromosome 13 Chromosome 13 is one of the 23 pairs of chromosomes in humans. People normally have two copies of this chromosome. Chromosome 13 spans about 114 million base pairs (the building material of DNA) and represents between 3.5 and 4% of the total DNA ...
.'' RB1'' was the first
tumor suppressor gene A tumor suppressor gene (TSG), or anti-oncogene, is a gene that regulates a cell during cell division and replication. If the cell grows uncontrollably, it will result in cancer. When a tumor suppressor gene is mutated, it results in a loss or re ...
cloned. Although'' RB1'' interacts with over 100 cell proteins, its negative regulator effect on the cell cycle principally arises from binding and inactivation of the
transcription factor In molecular biology, a transcription factor (TF) (or sequence-specific DNA-binding factor) is a protein that controls the rate of transcription of genetic information from DNA to messenger RNA, by binding to a specific DNA sequence. The f ...
''
E2F E2F is a group of genes that encodes a family of transcription factors (TF) in higher eukaryotes. Three of them are activators: E2F1, 2 and E2F3a. Six others act as suppressors: E2F3b, E2F4-8. All of them are involved in the cell cycle regulation a ...
'', thus repressing the transcription of genes which are required for the
S phase S phase (Synthesis Phase) is the phase of the cell cycle in which DNA is replicated, occurring between G1 phase and G2 phase. Since accurate duplication of the genome is critical to successful cell division, the processes that occur during ...
. The defective ''RB1 ''gene can be inherited from either parent; in some children, however, the mutation occurs in the early stages of fetal development. The expression of the'' RB1 ''
allele An allele (, ; ; modern formation from Greek ἄλλος ''állos'', "other") is a variation of the same sequence of nucleotides at the same place on a long DNA molecule, as described in leading textbooks on genetics and evolution. ::"The chrom ...
is
autosomal An autosome is any chromosome that is not a sex chromosome. The members of an autosome pair in a diploid cell have the same morphology, unlike those in allosomal (sex chromosome) pairs, which may have different structures. The DNA in autosom ...
dominant with 90%
penetrance Penetrance in genetics is the proportion of individuals carrying a particular variant (or allele) of a gene (the genotype) that also express an associated trait (the phenotype). In medical genetics, the penetrance of a disease-causing mutation is t ...
. Inherited forms of retinoblastomas are more likely to be bilateral. In addition, inherited uni- or bilateral retinoblastomas may be associated with
pineoblastoma Pineoblastoma is a malignant tumor of the pineal gland. A pineoblastoma is a supratentorial midline primitive neuroectodermal tumor. Pineoblastoma can present at any age, but is most common in young children. They account for 0.001% of all primary ...
and other malignant midline supratentorial
primitive neuroectodermal tumor Primitive neuroectodermal tumor is a malignant (cancerous) neural crest tumor. It is a rare tumor, usually occurring in children and young adults under 25 years of age. The overall 5 year survival rate is about 53%. It gets its name because the m ...
s (PNETs) with a dismal outcome; retinoblastoma concurrent with a PNET is known as
trilateral retinoblastoma Trilateral retinoblastoma is a malignant midline primitive neuroectodermal tumor occurring in patients with inherited uni- or bilateral retinoblastoma. In most cases trilateral retinoblastoma presents itself as pineoblastoma (pineal TRb). In about ...
. A 2014 meta-analysis showed that 5-year survival of trilateral retinoblastoma increased from 6% before 1995 to 57% by 2014, attributed to early detection and improved chemotherapy. The development of retinoblastoma can be explained by the two-hit model. According to the two-hit model, both alleles need to be affected, so two events are necessary for the retinal cell or cells to develop into tumors. The first mutational event can be inherited (
germline In biology and genetics, the germline is the population of a multicellular organism's cells that pass on their genetic material to the progeny (offspring). In other words, they are the cells that form the egg, sperm and the fertilised egg. They ...
or constitutional), which will then be present in all cells in the body. The second “hit” results in the loss of the remaining normal allele (gene) and occurs within a particular retinal cell. In the sporadic, nonheritable form of retinoblastoma, both mutational events occur within a single retinal cell after fertilization (somatic events); sporadic retinoblastoma tends to be unilateral. Several methods have been developed to detect the ''RB1'' gene mutations. Attempts to correlate gene mutations to the stage at presentation have not shown convincing evidence of a correlation.


MYCN

Not all retinoblastoma cases are with RB1 inactivation. There are cases reported with only one RB1 mutation or even two functional RB1 alleles, which indicates other oncogenic lesions of retinoblastoma. Somatic amplification of the '' MYCN''
oncogene An oncogene is a gene that has the potential to cause cancer. In tumor cells, these genes are often mutated, or expressed at high levels.
is responsible for some cases of nonhereditary, early-onset, aggressive, unilateral retinoblastoma. MYCN can act as a transcription factor and promotes proliferation by regulating the expression of cell cycle genes. Although ''MYCN'' amplification accounted for only 1.4% of retinoblastoma cases, researchers identified it in 18% of infants diagnosed at less than 6 months of age. Median age at diagnosis for ''MYCN'' retinoblastoma was 4.5 months, compared with 24 months for those who had nonfamilial unilateral disease with two ''RB1 ''gene mutations.


Diagnosis

Screening for retinoblastoma should be part of a "well baby" screening for newborns during the first 3 months of life, to include: * The
red reflex The red reflex refers to the reddish-orange reflection of light from the back of the eye, or fundus, observed when using an ophthalmoscope or retinoscope. The reflex relies on the transparency of optical media (tear film, cornea, aqueous humor, ...
: checking for a normal reddish-orange reflection from the eye's retina with an ophthalmoscope or retinoscope from about 30 cm or 1 foot, usually done in a dimly lit or dark room * The corneal light reflex or Hirschberg test: checking for symmetrical reflection of beam of light in the same spot on each eye when a light is shined into each cornea, to help determine whether the eyes are crossed *
Eye examination An eye examination is a series of tests performed to assess vision and ability to focus on and discern objects. It also includes other tests and examinations pertaining to the eyes. Eye examinations are primarily performed by an optometrist, ...
: checking for any structural abnormalities


Classification

The two forms of the disease are a
heritable Heredity, also called inheritance or biological inheritance, is the passing on of traits from parents to their offspring; either through asexual reproduction or sexual reproduction, the offspring cells or organisms acquire the genetic informa ...
form and nonheritable form (all cancers are considered genetic in that mutations of the genome are required for their development, but this does not imply that they are heritable, or transmitted to offspring). Around 55% of children with retinoblastoma have the nonheritable form. If no history of the disease exists within the family, the disease is labeled "sporadic", but this does not necessarily indicate that it is the nonheritable form. Bilateral retinoblastomas are commonly heritable, while unilateral retinoblastomas are commonly nonheritable. In about two-thirds of cases, only one eye is affected (unilateral retinoblastoma); in the other third, tumors develop in both eyes (bilateral retinoblastoma). The number and size of tumors on each eye may vary. In certain cases, the
pineal gland The pineal gland, conarium, or epiphysis cerebri, is a small endocrine gland in the brain of most vertebrates. The pineal gland produces melatonin, a serotonin-derived hormone which modulates sleep patterns in both circadian and seasonal cy ...
or the suprasellar or parasellar region (or in very rare cases other midline intracranial locations) is also affected (trilateral retinoblastoma). The position, size, and quantity of tumors are considered when choosing the type of treatment for the disease.


Differential diagnosis

:1. Persistent hyperplastic primary vitreous is a congenital developmental anomaly of the eye resulting from failure of the embryological, primary vitreous, and hyaloid vasculature to regress, whereby the eye is shorter, develops a cataract, and may present with whitening of the pupil. :2. Coats disease is a typically unilateral disease characterised by abnormal development of blood vessels behind the retina, leading to blood vessel abnormalities in the retina and retinal detachment to mimic retinoblastoma. :3.
Toxocariasis Toxocariasis is an illness of humans caused by the dog roundworm (''Toxocara canis'') and, less frequently, the cat roundworm ('' Toxocara cati'').https://academic.oup.com/ajcp/article/142/suppl_1/A104/1771175 Eosinophilic Pseudoleukemia Due to T ...
is a parasitic disease of the eye associated with exposure to infected puppies, which causes a retinal lesion leading to retinal detachment. :4. Retinopathy of prematurity is associated with low-birth-weight infants who receive supplemental oxygen in the period immediately after birth, and it involves damage to the retinal tissue and may lead to retinal detachment. :5.
Congenital Cataract Congenital cataracts refers to a lens opacity which is present at birth. Congenital cataracts cover a broad spectrum of severity: whereas some lens opacities do not progress and are visually insignificant, others can produce profound visual impa ...
:6.
Norrie Disease Norrie disease is a rare disease and genetic disorder that primarily affects the eyes and almost always leads to blindness. It is caused by mutations in the ''Norrin cystine knot growth factor (NDP)'' gene, which is located on the X chromosome. ...
If the eye examination is abnormal, further testing may include imaging studies, such as computerized tomography (CT),
magnetic resonance imaging Magnetic resonance imaging (MRI) is a medical imaging technique used in radiology to form pictures of the anatomy and the physiological processes of the body. MRI scanners use strong magnetic fields, magnetic field gradients, and radio wave ...
(MRI), and
ultrasound Ultrasound is sound waves with frequencies higher than the upper audible limit of human hearing. Ultrasound is not different from "normal" (audible) sound in its physical properties, except that humans cannot hear it. This limit varies ...
. CT and MRI can help define the structure abnormalities and reveal any calcium depositions. Ultrasound can help define the height and thickness of the tumor.
Bone marrow Bone marrow is a semi-solid biological tissue, tissue found within the Spongy bone, spongy (also known as cancellous) portions of bones. In birds and mammals, bone marrow is the primary site of new blood cell production (or haematopoiesis). It i ...
examination or
lumbar puncture Lumbar puncture (LP), also known as a spinal tap, is a medical procedure in which a needle is inserted into the spinal canal, most commonly to collect cerebrospinal fluid (CSF) for diagnostic testing. The main reason for a lumbar puncture is ...
may also be done to determine any
metastases Metastasis is a pathogenic agent's spread from an initial or primary site to a different or secondary site within the host's body; the term is typically used when referring to metastasis by a cancerous tumor. The newly pathological sites, the ...
to bones or the brain.


Morphology

Gross and microscopic appearances of retinoblastoma are identical in both hereditary and sporadic types. Macroscopically, viable tumor cells are found near blood vessels, while zones of necrosis are found in relatively avascular areas. Microscopically, both undifferentiated and differentiated elements may be present. Undifferentiated elements appear as collections of small, round cells with hyperchromatic nuclei; differentiated elements include
Flexner-Wintersteiner rosette In histopathology, a palisade is a single layer of relatively long cells, arranged loosely perpendicular to a surface and parallel to each other. A rosette is a palisade in a halo or spoke-and-wheel arrangement, surrounding a central core or hub. ...
s, Homer Wright rosettes, and fleurettes from photoreceptor differentiation. Image:Wardrop retinoblastoma.jpg, Drawing of a large retinoblastoma Image:Trilateral retinoblastoma.jpg, Aspect of trilateral retinoblastoma on MRI Image:Retinoblastoma ultrasound.jpg, An ocular ultrasound of a large retinoblastoma tumor within the eye of a 3-year-old boy Image:Retinoblastooma.jpg, Funduscopic finding of a retinoblastoma Image:Fundus retinoblastoma.jpg, Ocular fundus aspect of retinoblastoma Image:Retinoblastoma .jpg, Large exophytic white tumor with foci of calcification producing total exudative retinal detachment Image:Retinoblastoma rosette.jpg, Flexner-Wintersteiner rosettes in retinoblastoma Image:Rtbl400.GIF, Retinoblastoma, 400 X magnification Image:RB1.JPG, Crystal structure of the retinoblastoma tumor suppressor protein bound to E2F peptide polymer


Genetic testing

Identifying the ''RB1'' gene mutation that led to a child's retinoblastoma can be important in the clinical care of the affected individual and in the care of (future) siblings and offspring. It may run in the family. # Bilaterally affected individuals and 13-15% of unilaterally affected individuals, are expected to show an ''RB1'' mutation in blood. By identifying the ''RB1'' mutation in the affected individual, (future) siblings, children, and other relatives can be tested for the mutation; if they do not carry the mutation, child relatives are not at risk of retinoblastoma, so need not undergo the trauma and expense of examinations under anaesthetic. For the 85% of unilaterally affected patients found not to carry either of their eye tumor'' RB1'' mutations in blood, neither molecular testing nor clinical surveillance of siblings is required. # If the ''RB1'' mutation of an affected individual is identified, amniotic cells in an at-risk pregnancy can be tested for the family mutation; any fetus that carries the mutation can be delivered early, allowing early treatment of any eye tumors, leading to better visual outcomes. # For cases of unilateral retinoblastoma where no eye tumor is available for testing, if no ''RB1'' mutation is detected in blood after high-sensitivity molecular testing (i.e. >93%'' RB1'' mutation detection sensitivity), the risk of a germline ''RB1'' mutation is reduced to less than 1%, a level at which only clinic examination (and not examinations under anaesthetic) is recommended for the affected individual and their future offspring (National Retinoblastoma Strategy, Canadian Guidelines for Care).


Imaging

Traditional ultrasound B scan can detect calcifications in the tumour while high-frequency ultrasound B scan is able to provide higher resolution than the traditional ultrasound and determine the proximity of the tumour with front portion of the eye. MRI scan can detect high-risk features such as optic nerve invasion; choroidal invasion, scleral invasion, and intracranial invasion. CT scan is generally avoided because radiation can stimulate the formation of more eye tumours in those with RB1 genetic mutation.


Staging

In order to properly diagnose retinoblastoma, there must be guidelines to follow to properly classify the risk of the tumor. The ''Reese Ellsworth Classification System,'' by Dr. Algernon Reese and Dr. Robert Ellsworth, is universally used to determine the size, location, and multi-focality of the tumor. The system was originally used to decide the best treatment result by using external beam radiotherapy, as well as, the likeliness of salvaging the globe of the eye. Due to
chemotherapy Chemotherapy (often abbreviated to chemo and sometimes CTX or CTx) is a type of cancer treatment that uses one or more anti-cancer drugs (chemotherapeutic agents or alkylating agents) as part of a standardized chemotherapy regimen. Chemother ...
not being part of the ''Reese Ellsworth Classification System,'' there needed to be an updated classification system to foresee the treatment outcomes of chemotherapy. The International Classification for Intraocular Retinoblastoma is now the current system being used, and it was created by Murphree and associates. According to Reese and Ellsworth, there were different groups that had various features in order to classify the globe salvage as very favorable to the category of very unfavorable. In order to salvage the affected eye, the disc diameter had to be around 4DD and behind the equator to have higher favorability. If the tumor was around ten in disc diameter and involved roughly 50% of the retina, it was considered unfavorable to salvage the globe which could result in enucleation. According to Murphree, the different groups were classified from very low risk to very high risk which was determined by features of the given tumor. Very low risk means that the tumor has to be less than 3mm and there must be no seeding of the
vitreous Vitreous may refer to: Materials * Glass, an amorphous solid material ** Vitreous enamel, a material made by fusing powdered glass to a substrate by firing * Vitreous lustre, a glassy luster or sheen on a mineral surface Biology * Vitreous bod ...
or sub-retinal area. When a patient is very high risk, the tumor presents itself with multiple features and is going to have to be treated with conservative treatment modalities or enucleation. International Classification for Intraocular Retinoblastoma


Treatment

The priority of retinoblastoma treatment is to preserve the life of the child, then to preserve vision, and then to minimize complications or side effects of treatment. The exact course of treatment depends on the individual case and is decided by the ophthalmologist in discussion with the paediatric oncologist. Correct treatment also depends on the mutation type, whether it is a germline RB1 mutation, a sporadic RB1 mutation or MYCN amplification with functional RB1. Children with involvement of both eyes at diagnosis usually require multimodality therapy (chemotherapy, local therapies). The various treatment modalities for retinoblastoma includes: * Enucleation of the eye – Most patients with unilateral disease present with advanced intraocular disease, so usually undergo enucleation, which results in a cure rate of 95%. In bilateral Rb, enucleation is usually reserved for eyes that have failed all known effective therapies or without useful vision. *
External beam radiotherapy External beam radiotherapy (EBRT) is the most common form of radiotherapy (radiation therapy). The patient sits or lies on a couch and an external source of ionizing radiation is pointed at a particular part of the body. In contrast to brachy ...
(EBR) – The most common indication for EBR is for the eye in a young child with bilateral retinoblastoma who has active or recurrent disease after completion of chemotherapy and local therapies. However, patients with hereditary disease who received EBR therapy are reported to have a 35% risk of second cancers. *
Brachytherapy Brachytherapy is a form of radiation therapy where a sealed radiation source is placed inside or next to the area requiring treatment. ''Brachy'' is Greek for short. Brachytherapy is commonly used as an effective treatment for cervical, pro ...
involves the placement of a radioactive implant (plaque), usually on the sclera adjacent to the base of a tumor. It used as the primary treatment, or more frequently, in patients with small tumors or in those who had failed initial therapy including previous EBR therapy. *
Thermotherapy Heat therapy, also called thermotherapy, is the use of heat in therapy, such as for pain relief and health. It can take the form of a hot cloth, hot water bottle, ultrasound, heating pad, hydrocollator packs, whirlpool baths, cordless FIR h ...
involves the application of heat directly to the tumor, usually in the form of infrared radiation. It is also used for small tumors. * Laser photocoagulation is recommended only for small posterior tumors. An argon or diode laser or a xenon arc is used to coagulate all the blood supply to the tumor. *
Cryotherapy Cryotherapy, sometimes known as cold therapy, is the local or general use of low temperatures in medical therapy. Cryotherapy may be used to treat a variety of tissue lesions. The most prominent use of the term refers to the surgical treatment, s ...
induces damage to the vascular endothelium with secondary thrombosis and infarction of the tumor tissue by rapidly freezing it. It may be used as primary therapy for small peripheral tumors or for small recurrent tumors previously treated with other methods. * Systemic
chemotherapy Chemotherapy (often abbreviated to chemo and sometimes CTX or CTx) is a type of cancer treatment that uses one or more anti-cancer drugs (chemotherapeutic agents or alkylating agents) as part of a standardized chemotherapy regimen. Chemother ...
has become forefront of treatment in the past decade, in the search for globe-preserving measures and to avoid the adverse effects of EBR therapy. The common indications for chemotherapy for intraocular retinoblastoma include tumors that are large and that cannot be treated with local therapies alone in children with bilateral tumors. It is also used in patients with unilateral disease when the tumors are small, but cannot be controlled with local therapies alone. * Intra-arterial chemotherapy – Chemotherapeutic drugs are administered locally by a thin catheter threaded through the groin, through the aorta, and the neck, directly into the optic vessels. * Nanoparticulate chemotherapy – To reduce the adverse effects of systemic therapy, subconjuctival (local) injection of nanoparticle carriers containing chemotherapeutic agents (carboplatin) has been developed, which has shown promising results in the treatment of retinoblastoma in animal models without adverse effects. * Chemoreduction is a combined approach using chemotherapy to initially reduce the size of the tumor, and adjuvant focal treatments, such as transpupillary thermotherapy, to control the tumor.


Prognosis

In the developed world, retinoblastoma has one of the best cure rates of all childhood cancers (95-98%), with more than 90% of sufferers surviving into adulthood. In the UK, around 40 to 50 new cases are diagnosed each year. Good prognosis depends upon early presentation of the child in health facility. Late presentation is associated with a poor prognosis. Survivors of hereditary retinoblastoma have a higher risk of developing other cancers later in life.


Epidemiology

Retinoblastoma presents with cumulative lifetime incidence rate of one case of retinoblastoma per 18000 to 30000 live births worldwide. A higher incidence is noted in developing countries, which has been attributed to lower socioeconomic status and the presence of
human papilloma virus Human papillomavirus infection (HPV infection) is caused by a DNA virus from the '' Papillomaviridae'' family. Many HPV infections cause no symptoms and 90% resolve spontaneously within two years. In some cases, an HPV infection persists and r ...
sequences in the retinoblastoma tissue. Almost 80% of children with retinoblastoma are diagnosed before three years of age and diagnosis in children above six years of age is extremely rare. In the UK, bilateral cases usually present within 14 to 16 months, while diagnosis of unilateral cases peaks between 24 and 30 months.


See also

*
Eye cancer Eye neoplasms can affect all parts of the eye, and can be a benign tumor or a malignant tumor (cancer). Eye cancers can be primary (starts within the eye) or metastatic cancer (spread to the eye from another organ). The two most common cancers th ...
*
Eye examination An eye examination is a series of tests performed to assess vision and ability to focus on and discern objects. It also includes other tests and examinations pertaining to the eyes. Eye examinations are primarily performed by an optometrist, ...
* Retinoblastoma protein


References


External links


Retinoblastoma information
from
MedlinePlus MedlinePlus is an online information service produced by the United States National Library of Medicine. The service provides curated consumer health information in English and Spanish with select content in additional languages. The site brings ...
*
RB1 Mutation Database
*
NCBI Genetic Testing Registry
{{Eye tumors Ocular neoplasia Rare diseases Nervous system neoplasia Hereditary cancers Small-blue-round-cell tumors Pediatric cancers