Q) Retinoblastoma, the most common ocular malignancy of childhood, has the following features. Which statement is TRUE?
a) It is always unilateral and sporadic
b) Bilateral disease occurs in about one-third of cases
c) It is inherited in an autosomal recessive fashion
d) It is caused by mutation of the p53 gene on chromosome 17
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Correct Answer: b) Bilateral disease occurs in about one-third of cases
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Explanation:
- Retinoblastoma is the most common ocular malignancy in childhood.
- Approximately one-third of cases present as bilateral disease.
- About 50% of cases are hereditary, transmitted in an autosomal dominant fashion with incomplete penetrance.
- The causative mutation involves the RB1 tumor suppressor gene on chromosome 13q14, not p53.
- Children with hereditary retinoblastoma have an increased risk of secondary malignancies, especially osteosarcoma.