Question:
Retinoblastoma occurs bilaterally in what percentage of cases?
Retinoblastoma occurs bilaterally in what percentage of cases?
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Unilateral is about 70-75%, so bilateral makes up the rest.
Updated On: Jun 24, 2026
- 10 - 15%
- 15 - 20%
- 20 - 25%
- 25 - 30%
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The Correct Option is D
Solution and Explanation
Step 1: Retinoblastoma is the most common intraocular malignant tumour of childhood, usually affecting children aged 1-2 years, with no sex predilection.
Step 2: It is unilateral in about 70-75% of cases and bilateral in about 25-30% of cases. So the correct figure is 25-30%, which is option d.
Step 3: Bilateral disease is almost always hereditary. It follows Knudson's two-hit hypothesis with the RB tumour suppressor gene on chromosome 13 (13q14); the first hit is inherited in the germline and the second occurs postnatally. Sporadic unilateral disease requires both hits to occur postnatally.
Step 4: Hence the bilateral incidence is 25-30%.
Step 2: It is unilateral in about 70-75% of cases and bilateral in about 25-30% of cases. So the correct figure is 25-30%, which is option d.
Step 3: Bilateral disease is almost always hereditary. It follows Knudson's two-hit hypothesis with the RB tumour suppressor gene on chromosome 13 (13q14); the first hit is inherited in the germline and the second occurs postnatally. Sporadic unilateral disease requires both hits to occur postnatally.
Step 4: Hence the bilateral incidence is 25-30%.
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