Question

Retinoblastoma occurs bilaterally in what percentage of cases?

• A. 10 - 15%
• B. 15 - 20%
• C. 20 - 25%
• D. 25 - 30%

Hint:

Unilateral is about 70-75%, so bilateral makes up the rest.

Answer 1

The Correct Option is D

Step 1: Think of retinoblastoma in two buckets: the common sporadic form and the inherited form. The inherited form drives the bilateral cases.

Step 2: Roughly three-quarters of patients (70-75%) have one eye involved, while the remaining quarter (25-30%) have both eyes involved. That bilateral fraction is the value asked for, so option d (25-30%) fits.

Step 3: The reason bilateral disease clusters at about a quarter of cases is the germline RB1 mutation. With one defective RB allele already present in every retinal cell (first hit), the second hit happens easily and often in both eyes, explaining the bilateral and multifocal pattern of hereditary retinoblastoma.

Step 4: So bilaterality is seen in 25-30% of patients.
\[\boxed{25\text{-}30\%}\]