Which chromosomal abnormality is most commonly associated with Wilms tumor and is present in approximately 30–40% of bilateral cases?

Explanation

## Wilms Tumor: Chromosomal Associations **Key Point:** Deletion of chromosome 11p13 is the most frequent chromosomal abnormality in Wilms tumor, occurring in 30–40% of bilateral cases and associated with the WT1 (Wilms tumor suppressor gene 1) locus. ### WT1 Gene and WAGR Syndrome Loss of the WT1 gene on 11p13 is linked to: - **WAGR syndrome** (Wilms tumor, Aniridia, Genitourinary anomalies, Retardation) - Increased risk of bilateral Wilms tumor - Denys–Drash syndrome (WT1 mutations causing glomerulonephritis) ### Other Chromosomal Associations | Chromosomal Abnormality | Gene/Syndrome | Frequency | Clinical Significance | |---|---|---|---| | 11p13 deletion | WT1 | 30–40% (bilateral) | WAGR, Denys–Drash | | 11p15 loss of imprinting | WT2, IGF2 | 10–15% | Beckwith–Wiedemann syndrome | | Monosomy 7 | — | Rare | Associated with poor prognosis | | Trisomy 18 | — | Rare | Occasional association | **High-Yield:** The WT1 gene is a tumor suppressor; its loss predisposes to Wilms tumor development. Bilateral Wilms tumor cases have a higher frequency of WT1 mutations than unilateral cases. **Clinical Pearl:** Children with WAGR syndrome or Denys–Drash syndrome require regular renal ultrasound screening for early Wilms tumor detection. [cite:Robbins 10e Ch 8]