**Core Concept**
Wilms tumor, also known as nephroblastoma, is a type of cancer that primarily affects children. It arises from the immature cells of the kidney, typically in children under the age of 5. This tumor is associated with several genetic and environmental factors.

**Why the Correct Answer is Right**
Wilms tumor has been linked to several genetic syndromes, including **Bilateral Wilms tumor** (also known as **Drash syndrome**), **Denys-Drash syndrome**, and **WAGR syndrome** (Wilms tumor, Aniridia, Genitourinary anomalies, and mental **R**etardation). Additionally, children with **Beckwith-Wiedemann syndrome** have an increased risk of developing Wilms tumor. The exact mechanisms are not fully understood, but they are thought to involve **WT1** gene mutations or deletions.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because **Aniridia** is a genetic condition characterized by the absence or underdevelopment of the iris, but it is not typically associated with Wilms tumor. However, it is part of the WAGR syndrome.
**Option B:** This option is incorrect because **Familial adenomatous polyposis** (FAP) is a genetic disorder that predisposes individuals to colorectal cancer, not Wilms tumor.
**Option C:** This option is incorrect because **Li-Fraumeni syndrome** is a genetic disorder that increases the risk of developing various types of cancer, including breast cancer, brain tumors, and sarcomas, but it is not directly associated with Wilms tumor.

**Clinical Pearl / High-Yield Fact**
Be aware that children with **Bilateral Wilms tumor** have a worse prognosis than those with unilateral tumors, and they often require more aggressive treatment.

**Correct Answer: D.**