Recent advances in the understanding of retinoblastoma.

Two distinct disease entities are recognisable in retinoblastoma. In the commonest form of the condition a solitary tumour involves only one eye and may be of relatively late onset. Less frequently, multiple tumours are encountered and may involve both eyes. Onset tends to be early and this form of the disease is transmitted in an autosomal dominant fashion. Although in the genetically determined form of retinoblastoma all retinal cells contain abnormal genetic material, only a very few undergo neoplastic change. Individually, the resultant tumours are indistinguishable in terms of clinical appearance and response to treatment from those of non-genetic retinoblastoma. The intriguing similarities of the different forms of the tumour may be explained by a new hypothesis which suggests that retinoblastoma may result from the loss of a pair of suppressor genes. When present, this pair of genes may also have a suppressor effect for other types of tumour. Loss of this suppression for tumours other than retinoblastoma may explain why survivors of genetic disease are highly susceptible to second, non-ocular neoplasms. If the gene can be identified using DNA probes, antenatal diagnosis of those who inherit the retinoblastoma gene may be possible in certain families.