<prompt> Most common presenting feature of retinoblastoma-White reflexProptosisPhotophobiaPain  <response>: Ans. is a i.e., White reflex Retinoblastomao Retinoblastoma is the most common intraocular tumor in children. The tumor is confined to infancy and very young children 1-2 years. There is no sex predisposition. Retinoblastoma is unilateral in 70-75 of cases and bilateral in 25-30 of cases.Etiologyo Retinoblastoma gene RB gene is located on 14 band on the long arm of chromosome 12 13ql4. RB gene is a tumor supressor gene. Retinoblastoma develops when both the normal alleles of the RB genes are inactived or alteredAt is typical example of Knudsons two hit hypothesis. In Hereditary retinoblastoma first genetic change first hit in RB gene is inherited from an affected parent, where as second mutation second hit occurs in postnatal life and both alleles are lost. In non- hereditary retinoblastoma, both mutations first and second hits occur postnataly.Pathologyo The tumor arises from small round cells with large nuclei, i.e., it is a tumor of a group called small round blue cell tumors. Microscopic features of a well differentiated tumor include Flexner- wintersteiner rosettes specific for retinoblastoma, Homer- wright rosettes, pseudorosettes and fleurettes formation. There are areas of necrosis and calcification.Clinical featureso Retinoblastoma can present with following featuresLeukocoria or amauratic cats eye reflex this is the most common manifestation. The leukocoria or the white glow in the pupil is caused by reflection of light from the white intraocular tumor.Strabismus - second most common manifestationSecondary glaucomaRedeyeExcessive tearsBuphthalmos proptosisCorneal clouding due to elevated intraocular pressureDiscoloration of iris due to neovascularization of irisOrbital cellulitisPainful red eye usually associated with pseudohypopyon and or hyphaemia picture simulating iridocyclitis.o Spread of retinoblastoma to distant structures occurs :-Direct extension by continuity to the optic nerve and brain is common. Therefore, after enucleation optic nerve is always examined to see invasion of optic nerve, which helps to decide about postoperative chemoradiation.Lymphatic spread to preauricular lymph nodesMetastasis by blood stream to cranial and other bones. 