Retinoblastoma

Retinoblastoma (Rb) is a rare form of cancer that rapidly develops from the immature cells of a retina, the light-detecting tissue of the eye. It is the most common primary malignant intraocular cancer in children, and it is almost exclusively found in young children.Drawing of a large retinoblastomaAspect of trilateral retinoblastoma on MRIAn ocular ultrasound of a large retinoblastoma tumor within the eye of a 3-year-old boyFunduscopic finding of a retinoblastomaOcular fundus aspect of retinoblastomaGross pathology of retinoblastoma tumor in enucleated eye of 3-year-old femaleLarge exophytic white tumor with foci of calcification producing total exudative retinal detachmentFlexner-Wintersteiner rosettes in retinoblastomaRetinoblastoma, 400 X magnificationCrystal structure of the retinoblastoma tumor suppressor protein bound to E2F peptide polymer Retinoblastoma (Rb) is a rare form of cancer that rapidly develops from the immature cells of a retina, the light-detecting tissue of the eye. It is the most common primary malignant intraocular cancer in children, and it is almost exclusively found in young children. Though most children survive this cancer, they may lose their vision in the affected eye(s) or need to have the eye removed. Almost half of children with retinoblastoma have a hereditary genetic defect associated with retinoblastoma. In other cases, it is caused by a congenital mutation in the chromosome 13 gene 13q14 (retinoblastoma protein). The most common and obvious sign of retinoblastoma is an abnormal appearance of the retina as viewed through the pupil, the medical term for which is leukocoria, also known as amaurotic cat's eye reflex. Other signs and symptoms include deterioration of vision, a red and irritated eye with glaucoma, and faltering growth or delayed development. 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. Depending on the position of the tumors, they may be visible during a simple eye exam using an ophthalmoscope to look through the pupil. A positive diagnosis is usually made only with an examination under anesthetic (EUA). 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' disease. The presence of the photographic fault red eye in only one eye and not in the other may be a sign of retinoblastoma. A clearer sign is 'white eye' or 'cat's eye' (leukocoria). Mutation of genes, found in chromosomes, can affect the way in which cells grow and develop within the body. Alterations in RB1 or MYCN can give rise to retinoblastoma. In children with the heritable genetic form of retinoblastoma, a mutation occurs in the RB1 gene on chromosome 13. RB1 was the first tumor suppressor gene cloned. Although RB1 interacts with over 100 cell proteins, its negative regulator effect on the cell cycle principally arises from binding and inactivation of the transcription factor E2F, thus repressing the transcription of genes which are required for the S phase. The defective RB1 gene can be inherited from either parent; in some children, however, the mutation occurs in the early stages of fetal development. The expression of the RB1 allele is autosomal dominant with 90% penetrance.