All of the following are true for retinoblastoma except: March 2011
Ans. B: Always unilateral The fellow eye in retinoblastoma, is affected, independently, not by metastasis, in about one-fouh of the cases Retinoblastoma/ Rb It is a rapidly developing cancer that develops in the cells of retina In the developed world, Rb has one of the best cure rates of all childhood cancers (95-98%), with more than nine out of every ten sufferers surviving into adulthood Classification There are two forms of the disease; a heritable form and non-heritable 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). Approximately 55% of children with Rb have the non-heritable form. If there is no history of the disease within the family, the disease is labeled "sporadic", but this does not necessarily indicate that it is the non-heritable form. In about two thirds of cases, only one eye is affected (unilateral retinoblastoma); in the other third, tumours develop in both eyes (bilateral retinoblastoma). The number and size of tumours on each eye may vary. In ceain cases, the pineal gland is also affected (trilateral retinoblastoma). Signs and symptoms The most common and obvious sign of retinoblastoma is an abnormal appearance of the pupil, leukocoria, also known as amaurotic cat's eye reflex. Some children with retinoblastoma can develop a squint, commonly referred to as "cross-eyed" or "wall-eyed" (strabismus). Retinoblastoma presents with advanced disease in developing countries and eye enlargement is a common finding. 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's Disease. Frequency of retinoblastoma Most children are diagnosed before the age of five years old.In developed countries, bilateral cases usually present within the first year with the average age at diagnosis being 9 months. Diagnosis of unilateral cases peaks between 24 and 30 months. Cause of retinoblastoma In children with the heritable genetic form of retinoblastoma there is a mutation on chromosome 13, called the RB1 gene. The defective RB1 gene can be inherited from either parent; in some children, however, the mutation occurs in the early stages of fetal development. Inherited forms of retinoblastomas are more likely to be bilateral; in addition, they may be associated with pinealoblastoma (also known as trilateral retinoblastoma) with a dismal outcome. Differential diagnosis Persistent hyperplastic primary vitreous (PHPV): congenital developmental anomaly of the eye resulting from failure of the embryological, primary vitreous and hyaloid vasculature to regress, whereby the eye is shoer, develops a cataract, and may present with whitening of the pupil. Coat's disease: 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. Toxocara canis: an infectious disease of the eye associated with exposure to infected puppies, which causes a retinal lesion leading to retinal detachment. Retinopathy of prematurity (ROP): associated with low bih weight infants who receive supplemental oxygen in the period immediately after bih, it involves damage to the retinal tissue and may lead to retinal detachment. Morphology Gross and microscopic appearances of retinoblastoma are identical in both hereditary and sporadic types. Macroscopically, ble 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 rosettes, Homer-Wright rosettes, and fluerettes from photoreceptor differentiation Treatment The first priority is to preserve the life of the child, then to preserve the vision and thirdly to minimize any complications or side effects of the treatment. Many treatment options exist, including chemotherapy, cryotherapy, radioactive plaques, laser therapy, external beam radiotherapy and surgical removal of the eyeball. Any combinations of these treatments may be adopted.
Leucocoria is the most common presentation
Always unilateral
May have family history
Most common age group affected is 1-2 year