Retinoblastoma is the most common primary tumor of the eye that arises from the nuclear layer of the retina and accounts for about 3% of the cancers occurring in children younger than 15 years of age.
Retinoblastoma can occur in both hereditary (40%) and sporadic (60%) forms. Hereditary disease includes those patients with a positive family history and those patients who have inherited a germline mutation from an unaffected parent. It has been found associated with deletions or mutations of the "Retinoblastoma" gene on the q14band of chromosome 13. The germline form can manifest both as unilateral or bilateral disease. However, most unilateral disease are sporadic where as all bilateral diseases are hereditary. But, unilateral disease in an infant is more likely to be a hereditary condition. 95% of the diagnosed cases of Retinoblastoma occur before the age of 5 years.