Retinoblastoma in children
Last reviewed: 23.04.2024
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Retinoblastoma is the most common malignant neoplasm in pediatric ophthalmology. It is a congenital tumor of embryonic retinal structures, the first signs of which appear at an early age. Retinoblastoma can occur sporadically or be inherited.
The incidence of retinoblastoma varies within 1 per 15 000-30 000 live births. In the US, it is about 200 new cases per year, of which 40-60 are bilateral.
About 80% of cases of retinoblastoma are diagnosed before 3-4 years, the peak incidence falls on 2 years. Bilateral lesion is diagnosed earlier than one-sided.
Retinoblastoma is often combined with multiple congenital anomalies: cardiovascular malformations, cleft palate, cortical hyperostosis, imperfect dentinogenesis, family congenital cataract.
Retinoblastoma is known to the international oncological community as an almost ideal model for the study of carcinogenesis, especially its hereditary nature. The cause of this tumor is the mutation of both copies or the loss of the gene allele RB1 (suppressor gene located in the 13ql4 region), which leads to a violation of the control of the cell cycle, as the gene encodes a nuclear phosphoprotein with a molecular mass of 110 kDa, suppressing DNA replication. Retinoblastoma develops in 80-90% of carriers of the chromosomal defect, which reflects the model of development of malignant neoplasms "two-hits model", developed by Knudson. According to this model, hereditary malignant neoplasms develop with a germ-cell mutation in combination with a somatic mutation of a similar allele. For the development of non-hereditary cancer, two somatic mutations are needed. The first mutation, according to the Knudson theory, arises in the phase of prezigot, so the abnormal gene contains all the cells of the body. In the postzigot phase for tumorigenesis, only one mutation (somatic) is needed. This theory explains the development of the bilateral or multifocal form of the disease in patients with a hereditary anamnesis. The presence of an abnormal copy or loss of an allele in all cells of the body also explains the cause of earlier tumor development in patients with a family form of the disease. The necessity of two parallel somatic mutations during oncogenesis explains the prevalence of a unifocal tumor in patients with non-hereditary form of retinoblastoma.
Children with a family form of retinoblastoma (40% of all retinoblastomas) tend to develop a second neoplasm. As a rule, these are solid tumors that appear in 70% of cases in the irradiation zone, in 30% of cases - in other areas. The most common are sarcomas, including osteosarcoma.
Symptoms of retinoblastoma
The most frequently observed external signs are strabismus and leukocoria ("white" reflex of the fundus). On the retina, the tumor looks like one or a number of foci of whitish color. The tumor can grow endophytic, with penetration into all media of the eye, or exophytally, affecting the retina. Other symptoms are periorbital inflammation, fixed pupil, iris heterochromia. Loss of vision in young children may not be manifested by complaints. If there is no secondary glaucoma or inflammation, intraocular tumors are painless. The presence of a tumor in the anterior parts of the eyeball, like metastasis, is associated with a poor prognosis. The main ways of metastasis of retinoblastoma are contact on the optical nerve, along the optic nerve membranes, hematogenously (through the veins of the retina) and through endophytic germination into the orbit.
Diagnosis of retinoblastoma
The diagnosis of retinoblastoma is established on the basis of clinical ophthalmological examination, radiography and ultrasonography without pathomorphological confirmation. In the presence of a family history, children should be examined by an ophthalmologist immediately after birth.
To confirm the diagnosis and determine the extent of the lesion (including detection of the tumor of the pineal region) CT or MRI of the orbit is recommended.
Treatment of retinoblastoma
Retinoblastoma is one of the solid tumors of childhood, most successfully treated with timely diagnosis and therapy using modern methods (brachytherapy, photocoagulation, thermochemotherapy, cryotherapy, chemotherapy). Overall survival, according to various literature data, varies from 90 to 95%. The main causes of death in the first decade of life (up to 50%) are the development of an intracranial tumor synchronously or metachronically with retinoblastoma, a poorly controlled tumor metastasis beyond the CNS, the development of additional malignant neoplasms.
The choice of method of treatment depends on the size, location and number of foci, the experience and capabilities of the medical center, the risk of involving the second eye. Most children with unilateral tumors have a fairly advanced stage of the disease, often without the possibility of preserving the vision of the affected eye. That is why enucleation often becomes the method of choice. If the diagnosis is made early, alternative treatment may be undertaken in an effort to preserve vision - photocoagulation, cryotherapy or radiation.
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