Contributors:Patricia Nguyen, MScBMC, Evan Debevec-McKenney, Ahmed A. Abu Ajeene, Kimberly Clay BSN, RN
With retinoblastoma, retino- refers to the retina of the eye and -blastoma means arising from embryonic tissue. So, retinoblastoma describes a malignant tumor of the retina that arises from embryonic retinal cells; and it typically affects children younger than 5 years of age.
Now, let’s quickly review the physiology of the retina, which is a thin layer of nerve cells that lie at the back of the eye. This layer houses blood vessels, as well as nerve cells called photoreceptors, which receive light and convert it into neural impulses. These impulses are then directed to the visual cortex of the brain, where they get translated into images.
Now, the cause of retinoblastoma is rooted in genetics, specifically, inactivation mutations of a tumor suppressor gene called RB1, which can be the result of an inherited germline mutation or a spontaneous mutation. Spontaneous mutations means that both RB1 mutations occur spontaneously in the somatic cells of the individual, and typically cause retinoblastoma in only one eye. On the other hand, inherited mutations usually cause multiple tumors in both eyes.
Lastly, risk factors for retinoblastoma include advanced paternal age, family history of retinoblastoma or a known RB1 gene mutation in one parent, paternal exposure to radiation, in addition to maternal exposure to diesel or gasoline exhaust during pregnancy.
Now, the pathology of retinoblastoma starts with mutations to the RB1 gene, which cause unregulated growth of retinal cells. Over time, these cancerous cells form a tumor in the retina, which can then invade nearby structures. Left untreated, retinoblastoma can metastasize to the brain, opposite eye, lymph nodes, bone, bone marrow, and to the liver. Other complications of retinoblastoma include blindness, retinal detachment, and secondary tumors, which are typically sarcomas.
Typically, the clinical manifestations of retinoblastoma start by the age of one year in cases of bilateral involvement, and by the age of three years in cases of unilateral involvement. The first symptom of retinoblastoma noticed by the parents is leukocoria, also called the cat’s eye reflex, meaning the pupil appears white instead of red as the light reflects off the tumor white surface. Other signs and symptoms of retinoblastoma include strabismus, ocular inflammation, which can cause pain and a red eye, in addition to visible extraocular growth, decreased vision, restricted eye movements, and protrusion of the eyeball, called proptosis.
The diagnosis of retinoblastoma starts with the client's history and physical assessment, followed by diagnostic tests. These tests include red reflex examination using an ophthalmoscope, which will show leukocoria; direct ophthalmoscopic examination, which will show a retinal mass;
as well as slit lamp examination may identify blood or tumor debris in the anterior chamber.
An ocular ultrasound can also be done to evaluate the size of the tumor; an MRI of the orbits and brain can reveal if there is tumor extension outside the eye;
and genetic testing can also be done.
Finally, eye examinations for all newborns and children should be done at routine child care for early detection; and clients with a family history of retinoblastoma should undergo genetic screening to determine if frequent clinical monitoring for retinoblastoma is needed.