**Core Concept:** Retinoblastoma is a rare malignant tumor of the retina that primarily affects children, and it is typically caused by mutations in the RB1 gene, leading to uncontrolled cell growth and division. The RB1 gene is responsible for regulating cell growth and preventing cancer.

**Why the Correct Answer is Right:** Retinoblastoma presents in children due to the fact that the tumor develops from retinal cells, which are actively dividing during childhood. Mutations in the RB1 gene lead to the loss of function of the tumor suppressor protein encoded by the gene. This results in uncontrolled cell growth and division, ultimately forming the retinoblastoma tumor.

**Why Each Wrong Option is Incorrect:**

A. While retinoblastoma can occur in adults, the overwhelming majority of cases develop in children, making it less likely than option C.
B. Although the RB1 gene is involved in cancer development, other factors like environmental exposures can contribute to retinoblastoma, making C the correct answer.
D. Retinoblastoma is not exclusively associated with genetic disorders like certain types of leukemia, making D incorrect.

**Clinical Pearl:** In cases where retinoblastoma is suspected, genetic testing should be performed to identify RB1 gene mutations, allowing for early intervention and treatment options.

**Correct Answer:** C. Retinoblastoma is a genetic disorder associated with mutations in the RB1 gene, which is more likely to occur in children.