Wilms tumor (Nephroblastoma)

Wilms’ tumor is a rare kidney cancer that primarily affects children. Also known as nephroblastoma, it’s the most common cancer of the kidneys in children. Wilms’ tumor most often affects children ages 3 to 4 and becomes much less common after age 5. Wilms’ tumor most often occurs in just one kidney, though it can sometimes be found in both kidneys at the same time.


  • Peak incidence: 2–5 years
  • Most common malignant neoplasm of the kidney in children


The exact etiology of Wilms tumor remains unknown, but it is associated with several genetic mutations and syndromes.

Genetic predisposition
  • Gene mutations have been found in children both with and without genetic syndromes who have Wilms tumor.
  • The WT1 (Wilms tumor 1) gene is the most important Wilms tumor gene (mutated in ∼ 10–20% of cases)
Associated syndromes
  • Approx. 10% of Wilms tumors occur in children with syndromes.
  • Denys-Drash syndrome (point mutation in WT1 gene, which encodes a zinc finger transcription factor)
    • Wilms tumor
    • Pseudohermaphroditism, undescended testes in males (due to gonadal dysgenesis)
    • Early-onset nephrotic syndrome
  • WAGR syndrome (deletion of the 11p13 band → deletion of WT1 gene and other genes such as PAX6)
    • Wilms tumor
    • Aniridia
    • Genitourinary (GU) anomalies – Pseudohermaphroditism, undescended testes in males (due to gonadal dysgenesis) and early onset nephrotic syndrome
    • Intellectual disability (mental Retardation)
  • Beckwith-Wiedemann syndrome (mutations of WT2 gene)

Clinical features

  • Abdominal mass (often found incidentally) which is non-tender, unilateral, not crossing midline (however, up to 10% of cases are bilateral and/or multifocal), smooth and firm.
  • Other signs and symptoms include
    • Abdominal pain (∼ 40% of cases)
    • Hematuria (∼ 25% of cases)
    • Hypertension (∼ 25% of cases)
    • In cases of subcapsular hemorrhage: anemia, and possibly fever
    • Symptoms caused by metastatic spread (e.g., pulmonary symptoms)


  • Urinalysis: hematuria may be present
  • Imaging
    • Best initial test: USG (Hypervascular tumor, mostly uniform echogenicity with hypoechoic areas of necrosis)
    • Abdominal CT/MRI: assess extent of involvement and help with surgical planning
    • CT thorax/CXR: determine metastases and staging
    • Biopsy is usually reserved for assessing nodules


Wilms tumor consists of embryonic glomerular structures and may include cysts, hemorrhage, or necrosis. It typically has a pseudocapsule.


Differential Diagnosis



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