Composed of primitive small round retinal cells

• Malignant ocular tumor of retinal cells
• Usually occurs before the third year of life

WordNet Word definitions in WordNet
n. malignant ocular tumor of retinal cells; usually occurs before the third year of life; composed of primitive small round retinal cells

Wiktionary Word definitions in Wiktionary
n. (context pathology English) A malignant tumour of the retina; a hereditary condition found mostly in children.

Wikipedia Word definitions in Wikipedia
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 malignant cancer of the eye in children, and it is almost exclusively found in young children. ...