Retinoblastoma is associated with which chromosome?

(A) 13 # RETINOBLASTOMA is a proliferation of neural cells which have failed to evolve normally.> Tumour is confined to infants and very young children and is frequently congenital> Retinoblastoma is directly associated with a genetic abnormality--deletions or mutation of the ql4 band of chromosome 13> Growth consists chiefly of small round cells with large nuclei resembling the cells of the nuclear layers of the retina.> Child is usually brought to the surgeon on account of a peculiar yellow reflex from the pupil, sometimes called leucocoria or 'amaurotic cat's eye> Clinically a cauliflower-like mass arising from the retina is seen extending into the vitreous> Calcification occurs in 75% of cases and is almost pathognomonic of retinoblastoma> X-rays can demonstrate calcification within the tumour, but a computerized tomography scan is more sensitive, as it also delineates the tumour and extension, if any, more thoroughly.> Treatment of small tumours is by local modalities such as cryotherapy for anterior lesions, photocoagulation for posterior ones, brachytherapy with 60Co or 1251 can also be used.> Treatment options for large tumours are Enucleation of the eye, External beam radiation therapy.> External beam radiotherapy confines the radiation to the affected sectors of the posterior segment of the globe and thus avoids damage to the lens and surrounding retina.> Prognosis of retinoblastoma, if untreated, is always bad, and the patient invariably dies.> Prognosis is fair if extraocular extension is avoided.