Sunday, 11 June 2017

Retinoblastoma Clinical | DNB Based MCQ

NIME Next Batch PGI Quest in Delhi from 10 August to 20 August


A patient has retinoblastoma. He is also likely to develop Mandibular osteosarcoma if the pathogenetic causes are the following EXCEPT 

A. p53 gene mutation 
B. Radiation induced 
C. Chemotherapy induced 
D. Mutation of Rb gene

Ans. C. (chemotherapy induced)
Explanation
1. Patients with hereditary retinoblastomas have up to 1,000 times greater risk of subsequently developing osteosarcoma, attributed to germ-line mutations in the RB gene.
2. Loss of heterozygosity, structural rearrangements, or point mutations in the RB gene is also present in 60 70% of sporadic tumors.
3. “Abnormalities in genes that regulate cell cycling, such as p53, CDK4, p16, 11JK4A, CYCLIN Dl, and MDM2 have also been implicated in the genesis of nonhereditary osteosarcomas”— Robbin’s
4. “The risk of osteosarcoma developing in facial bones increases greatly if external beam irradiation has been used to treat the retinoblastoma” Kanski
5. Osteogenic sarcoma is the most common second malignant neoplasm in survivours of familial or bilateral retinoblastomas. This disease is caused by a genetic mutation in Rb give on chromosome 13, which only increases the risk of de novo osteosarcoma but also potentiates the osteosarcoma—inducing ability of ionizing radiation.