What is a Wilms Tumor?
Wilms tumor (nephroblastoma) is the most common primary malignant renal tumor of childhood, accounting for approximately 90% of all childhood renal malignancies and 5-6% of all pediatric cancers. 1, 2
Pathophysiology and Origin
Wilms tumor is an embryonal malignancy that develops from remnants of immature kidney tissue that persist after normal renal development is complete 2, 3
The tumor histologically mimics renal embryogenesis and is composed of a variable mixture of three elements: stromal, blastemal, and epithelial components 3
Nephrogenic rests are considered precursor lesions and represent foci of embryonic metanephric tissue that abnormally persist after completion of kidney development 3
Clinical Presentation
The most common presentation is an abdominal mass or swelling, often discovered incidentally without other accompanying signs or symptoms 1
The nonspecific nature of symptoms can delay timely diagnosis and treatment 1
Approximately 500 new cases are diagnosed annually in the United States 2
Genetic Basis and Predisposition
Less than 50% of children with bilateral Wilms tumors have identified predisposition syndromes, though bilateral disease occurs earlier in life than unilateral disease 4
The most common single predisposition syndrome is Beckwith-Wiedemann syndrome (BWS) 4
Disorders involving WT1 pathogenic variants are more common in children with bilateral Wilms tumors 4
Emerging genetic predispositions include variants in REST, TRIM28, DIS3L2, and CTR9 genes 4
Children with bilateral disease have a "field defect" in their kidneys with clonal nephrogenesis and increased DNA methylation at the H19 locus on chromosome 11p15.5, putting them at higher risk for subsequent tumors even after treatment 4
Prognosis
Current long-term survival rates approach 85% overall, with many low-stage tumors achieving significantly higher survival rates 5
This represents dramatic improvement from only 30% survival in the early 20th century 5
Most patients now achieve survival rates exceeding 90% through multimodal therapy including surgery, chemotherapy, and radiation given according to risk stratification 2
Surveillance Considerations
For patients with genetic predisposition syndromes (WT1, Beckwith-Wiedemann, or DICER1), renal ultrasound surveillance is recommended, though specific frequency varies by syndrome 6
Children treated for bilateral Wilms tumor require ongoing surveillance with abdominal ultrasounds every 3 months until at least 8 years of age, regardless of whether they have syndromic features or harbor variants in known predisposition genes 4
Females with bilateral disease face higher risk for subsequent Wilms tumors compared to males 4