You are a helpful, respectful, and honest assistant. Always answer as helpfully as possible, while being safe. Your answers should not include any harmful, unethical, racist, sexist, toxic, dangerous, or illegal content. Please ensure that your responses are socially unbiased and positive in nature. If a question does not make any sense or is not factually coherent, explain why instead of answering something not correct. If you don't know the answer to a question, please don't share false information.
What is Gene for retinoblastoma is found on which chromosome and explain in detail?
(A) (13) (300- Khurana 5th)* Retinoblastoma appears to result from loss or inactivation of both normal alleles of the retinoblastoma gene (a DNA sequence located on long arm chromosome 13, the q 14 region)* It is the most common primary intraocular malignancy of childhood (Remember MC orbital malignancy of childhood is Rhabdomyosarcoma)* Knudson's proposed ''two- hit *' hypothesis of oncogenesis for Retinoblastoma Retinoblastoma | ||Heritable (germine)Non Heritable (somatic)* 40% tumours* Bilateral multifocal tumours* Predisposition ot second non ocular cancersPineloblastoma** osteosarcoma**** 60% tumours* Unilateral* Presence of leukoria (white pupillary reflex) and calcification within the globe in a one and half year old child is almost diagnostic of retinoblastoma* Most common presentation of Retinoblastoma is leukocorea or amauratic cat *s eye reflex and strabismus *** Other presentations(i) Secondary glaucoma(ii) Red eye(iii) Buphthalmos & proptosis(iv) Orbital cellulitis(v) Painful red eye usually associated with pseudohypopyon and (hyphaema( picture stimulating iridocyclitis)(vi) Excessive tearing(vii) Corneal clouding due to elevated IOP(viii) Discolouration of iris due to neovascularization of iris* LDH Is grossly increased in Retinoblastoma (where the aqueous (plasma ratio of LDH is greater than 1.5)* Ultrasound & CT scan are able to detect a intraocular mass with calcification, which is pathognomic of retinoblastoma.* MRI is not able to detect the calcification as wall as CT but it is investigation of choice to study the optic nerve & sellar and parasellar regions of the brain.* The most common method of spread of retinoblastoma is by direct invasion of optic nerve with extension in to theCNS, Hematogenous spread may lead to distant metastasis throughout the body.* Rosettes are characteristic in retinoblastoma