This is a rare tumour of childhood, which arises not from the choroid but, as its name suggests, from the retina. It is, however, the commonest primary intraocular tumour in children,with an incidence of one in 15,000 live births. It shows certain rather strange and unusual features. It is not usually present from birth, but occurs most frequently in infancy to age three years (although it can occur in older patients); it is either inherited as an autosomal dominant trait or can be sporadic in nature. Approximately 40% of cases are considered to be inherited. In one-third of inherited cases it appears in both eyes. A change in the RB1 gene on chromosome 13 is found in the inherited cases. Initially, it can be seen in an individual, suspected on account of the family history, as a small white, raised mass. Examination under anaesthesia is essential in such cases because the tumour might be in the extreme periphery of the fundus. A larger tumour can present as a white mass in the pupil ("leucocoria") and such an appearance in infancy demands immediate referral to an ophthalmologist (Figure 15.2). Other presenting features include strabismus, secondary glaucoma, proptosis or intraocular inflammatory signs. Computed tomography (CT) scanning and ultrasound might show a calcified intraocular mass. Extension tends to occur locally along the optic nerve and enucleation is often life saving. Until recently, enucleation was the treatment of choice and cure rates of 90-95% were achieved. Nowadays, eye-sparing therapy is preferred, in an attempt at avoiding the physical and psychological trauma involved in enucleating a young child. Alternative treatment options include initial systemic tumour chemoreduction with carboplatin-based regimens, followed by external beam radiotherapy, plaque radiotherapy, cryotherapy or laser photocoagulation. Genetic counselling is essential for these patients in order to prevent the increasing incidence of the tumours, which will result from effective medical treatment.

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