Wilm’s Tumor (Nephroblastoma) : Quick review

Wilm’s tumor is the most common primary renal tumor of childhood.

Origin: Embryonic nephrogenic (mesodermal) cells

Mechanism: Deletion of WT-1 gene on chromosome 11

Pathology:

a. Macroscopic (Gross): large, solitary tan to grey color mass; pale on cut section with areas of hemorrhage; 10% are bilateral or multicentric; grossly difficult to distinguish from neuroblastoma

b. Microscopic: tumor containing 3 elements –

1. Metanephric blastema
2. Epithelial elements (Immature glomeruli and tubule)
3. Stroma

Incidence: 1 per 10,000 children before the age of 15 years

Average age at diagnosis: 3-4 years

Symptoms:

1. Usually asymptomatic abdominal mass (classic history – found during dressing or bathing)
2. 20% patients present with minimal blunt trauma to mass
3. Other: abdominal mass, gross hematuria, fever

Signs:

1. Abdominal mass (mostly donot cross the midline)
2. Hematuria (10-15%; indicates invasion of collecting system)
3. Hypertension (20%; related to compression of juxtaglomerular apparatus)
4. Signs of Beckwith-Wiedemann syndrome may be present

Associated syndromes:

Approx. 10% of Wilms tumors occur in children with syndromes.

1. WAGR syndrome (deletion of WT1 gene)

• Wilms tumor
• Aniridia
• Genitourinary (GU) anomalies
• Intellectual disability (mental Retardation)

2. Beckwith-Wiedemann syndrome (mutations of WT2 gene)

Others: Denys-Drash syndrome (WT1), Fraiser syndrome (WT1), Neurofibromatosis

Best initial test: Ultrasonography of abdomen

Diagnostic radiological tests: Abdominal and chest CT –

1. Staging purpose
2. Preoperative assessment
3. Look at the contralateral kidney

Staging:

• Stage I: Limited to kidney and completely resected
• Stage II: Extends beyond kidney but completely resected; capsule invasion and perirenal tissue may be involved
• Stage III: Residual non-hematogenous tumor after resection
• Stage IV: Hematogenous metastases (lung, distal lymph nodes and brain)
• Stage V: Bilateral renal involvement

Best indicators of survival:

1. Stage
2. Histologic subtype: 85% have Favorable Histology (FH) with overall survival of 85% for all stages; 15% have Unfavorable Histology (UH)

Treatment:

Radical resection of affected kidney followed by:

1. Lower grade tumors (I and II): Chemotherapy (Actinomycin D, i.e. DACT and Vincristine)
2. Higher grade tumors (III and above): Radiotherapy

Routine pre-operative biopsy should be avoided as this upstages the tumor, requiring the intensification of chemotherapy and abdominal irradiation.

Neoadjuvant chemotherapy/radiotherapy may be required to regress the size of tumor before surgery.

This is a quick review of Wilm’s tumor on request of final year MBBS student Jaymala Shelke. For detailed information on Wilm’s tumor, refer to the textbooks.