What is the diagnostic and treatment approach for a pediatric patient suspected of having Wilm's tumor?

Diagnostic and Treatment Approach for Wilms Tumor

For a pediatric patient suspected of having Wilms tumor, initiate evaluation with abdominal ultrasound as the first-line imaging modality, followed by CT or MRI for staging, and proceed directly to upfront nephrectomy without pre-operative biopsy for unilateral tumors per North American Children's Oncology Group protocols. 1

Initial Diagnostic Imaging

Ultrasound is the optimal initial screening tool because it is widely available, lacks ionizing radiation, can be performed without sedation, and has high sensitivity for detecting renal masses. 1 The ultrasound should:

• Confirm the renal origin of the mass 1
• Evaluate the inferior vena cava for tumor extension using Doppler 1
• Examine the bladder for additional lesions 1
• Assess the contralateral kidney for bilateral disease 2

Advanced Imaging for Staging

After ultrasound confirmation, proceed with cross-sectional imaging:

• CT or MRI is required for complete staging and surgical planning 3, 4
• MRI is preferred when evaluating bilateral tumors, detecting nephrogenic rests, and planning nephron-sparing surgery 2, 1
• CT scan reveals concomitant lesions, abdominal vessel involvement, and lymph node status 3
• Assess for metastatic disease, particularly pulmonary metastases (present in 44.4% of Wilms tumor at presentation) 5

Critical imaging features to document:

• Tumor size and laterality (bilateral disease occurs in a significant subset) 2
• Vascular involvement (encasement, tumor thrombus) 2, 3
• Lymphadenopathy 3
• Infiltration of adjacent structures 2
• Central location and collecting system involvement 2
• Tumor rupture 2

Surgical Management

For unilateral tumors, proceed directly to upfront nephrectomy without pre-operative biopsy, as biopsy risks tumor spillage and upstaging, which necessitates more intensive chemotherapy and radiation. 1

For syndromic or bilateral Wilms tumor, nephron-sparing surgery is recommended when feasible given the increased recurrence risk in the ipsilateral or contralateral kidney. 2 MRI is the ideal imaging modality for pre-operative evaluation when considering partial nephrectomy. 2

Genetic Testing

Universal genetic testing and genetic counseling should be offered to all children with bilateral Wilms tumors. 2 Testing should include:

• Methylation and copy-number analysis of chromosome 11p15.5 2
• Sequencing and copy-number analysis of WT1 2
• Testing for common predisposition genes: REST, TRIM28, DIS3L2, and CTR9 2

Genetic testing should also be pursued in patients with bilateral tumors, as they often represent genetic predisposition syndromes. 1

Surveillance Protocols

For children with bilateral Wilms tumors (regardless of syndromic features or identified genetic variants), ongoing tumor surveillance with abdominal ultrasounds every 3 months until at least 8 years of age is recommended. 2 This is based on evidence that these kidneys have a "field defect" putting them at risk for subsequent tumors. 2

For children with identified genetic predisposition syndromes (TRIM28, REST, DIS3L2, CTR9 pathogenic variants):

• Renal ultrasound surveillance every 3 months from diagnosis until 8 years of age 2, 1
• Cascade testing for family members when pathogenic variants are identified 1

Note: Females with bilateral disease appear to be at higher risk for subsequent Wilms tumors than males. 2

Chemotherapy

Vincristine is FDA-approved for use in Wilms tumor and has been shown to be useful in combination with other oncolytic agents. 6 Treatment should be given according to risk stratification based on surgical staging and histology. 7, 8

Critical Pitfalls to Avoid

• Do not perform pre-operative biopsy on unilateral tumors - this risks tumor spillage and upstaging 1
• Do not miss bilateral disease - always evaluate the contralateral kidney carefully 2, 1
• Do not overlook genetic predisposition syndromes - 16% of children with Wilms tumor have at least one clinical feature of Beckwith-Wiedemann syndrome 2
• Do not fail to document vascular involvement - tumor thrombus and vascular encasement affect surgical approach 2, 3
• Do not skip surveillance in bilateral disease - even without identified genetic variants, these children require ongoing monitoring 2

Expected Outcomes

With current multimodal therapy including surgery, chemotherapy, and radiation given according to risk stratification, survival rates exceed 90%. 7, 8, 4