Wilms' Tumour (Nephroblastoma)
Summary
Wilms' Tumour (Nephroblastoma) is the most common renal malignancy in children. It is an embryonal tumour derived from the metanephros (precursor kidney tissue). Classically it presents as an asymptomatic abdominal mass discovered by parents while bathing the child. With modern multimodal therapy, it is one of the great success stories of paediatric oncology, with cure rates exceeding 90%. [1,2]
Clinical Pearls
"Do Not Palpate": Once a Wilms tumour is suspected, put a sign over the bed saying "DO NOT PALPATE". Heavy-handed examination can cause the tumour capsule to rupture, spilling cancer cells into the peritoneum. This automatically upstages the tumour to Stage III (requires radiation), significantly increasing toxicity.
WAGR Syndrome: A key genetic association (deletion of chromosome 11p13).
- W: Wilms' Tumour.
- A: Aniridia (Absence of the iris).
- G: Genitourinary anomalies (Hypospadias, Cryptorchidism).
- R: Range of developmental delay (formerly Retardation).
Beckwith-Wiedemann Syndrome: Overgrowth syndrome. Macroglossia (big tongue), Macrosomia (big body), Omphalocele, Hemihypertrophy (one leg bigger than the other). These kids need screening ultrasounds every 3 months.
Incidence
- 1 in 10,000 children.
- 5% are bilateral (synchronous or metachronous).
- Peak Age: 2-5 years old. (Rare after age 15).
Genetics
- WT1 Gene (11p13): Associated with WAGR.
- WT2 Gene (11p15): Associated with Beckwith-Wiedemann.
Histology
- Triphasic Histology: Contains three cell types:
- Blastemal: Undifferentiated small blue cells.
- Epithelial: Tubules/Glomeruli structures.
- Stromal: Muscle/Cartilage/Bone.
- Anaplasia: Presence of large, hyperchromatic nuclei (p53 mutation). This is "Unfavourable Histology" and is harder to treat.
| Feature | Wilms Tumour | Neuroblastoma |
|---|---|---|
| Origin | Kidney | Adrenal / Sympathetic chain |
| Laterality | Usually Unilateral | Crosses Midline often |
| Consistency | Smooth, firm | Irregular, craggy |
| Child | Well, happy | Sick, malaise, bone pain |
| Calcification | Rare (less than 10%) | Common (50%) |
| Metastases | Lung | Bone / Bone Marrow |
History
Signs
Imaging
- Ultrasound: First line. Confirms renal origin (vs adrenal/liver). Checks patency of the IVC (tumour thrombus).
- CT/MRI Chest/Abdo: Staging.
- Claw Sign: Normal kidney tissue splayed around the tumour like a claw (suggests renal origin).
Lab
- Urine: Haematuria. VMA/HVA (rule out Neuroblastoma).
- Biopsy: Contraindicated in most cases (UK/Europe). Risk of needle track seeding. Diagnosis is based on typical radiological features. Biopsy is only done if presentation is atypical (e.g. older child >10y).
Management Algorithm (SIOP Protocol - UK/Europe)
SUSPECTED RENAL MASS
↓
IMAGING (US / CT / MRI)
(Confirm renal origin + Staging)
↓
PRE-OPERATIVE CHEMOTHERAPY
(Vincristine + Actinomycin D for 4-6 weeks)
(Goal: Shrink tumour + reduce rupture risk)
↓
NEPHRECTOMY
(Radical Nephroureterectomy)
(+ Lymph node sampling)
↓
PATHOLOGICAL STAGING
& HISTOLOGY GRADING
↓
┌───────────┴───────────┐
LOW RISK HIGH RISK
(Stage I/II) (Stage III/IV/Anaplasia)
↓ ↓
NO FURTHER RX POST-OP CHEMO
(or mild chemo) + RADIOTHERAPY
1. SIOP vs COG
- SIOP (Europe/UK): Chemo THEN Surgery. Believes shrinking tumour makes surgery safer.
- COG (North America): Surgery THEN Chemo. Believes accurate staging requires intact tumour.
- Outcome data is similar for both.
2. Surgery
- Radical Nephrectomy.
- Nephron Sparing Surgery: Used only for bilateral tumours or solitary kidney.
3. Chemotherapy Agents
- "VA" regimen: Vincristine + Actinomycin D.
- "VAD" regimen: + Doxorubicin (for high stage).
- Tumour Rupture: Upstages disease.
- Veno-Occlusive Disease (VOD): Hepatic toxicity from Actinomycin D.
- Cardiomyopathy: From Doxorubicin (Anthracycline).
- Second Malignancy: Risk from Radiotherapy.
- Renal Failure: Especially if bilateral.
- Overall Survival: >90%.
- Recurrence: Usually occurs within 2 years.
Key Guidelines
| Guideline | Organisation | Key Recommendations |
|---|---|---|
| Renal Tumours | SIOP-RTSG (2016) | Pre-operative chemotherapy (4-6 weeks) is standard of care in Europe. |
| Follow-Up | CCLG | Surveillance of the remaining kidney. |
Landmark Studies
1. SIOP 2001 Trial
- Confirmed efficacy of preoperative chemo in reducing tumour volume and intraoperative rupture rates compared to immediate surgery.
What is Wilms Tumour?
It is a type of kidney cancer that affects children. It happens when some of the cells that were supposed to grow into the kidney before birth stay "immature" and grow into a lump instead.
Is it hereditary?
Usually not. 95% of cases happen by chance. Only a small number (like those with WAGR or Beckwith-Wiedemann) are genetic.
What is the treatment?
In the UK, we usually give chemotherapy first to shrink the lump. This makes the operation to remove the kidney much safer. Removing one kidney is fine - the other one takes over the work completely.
Will they survive?
Yes. Wilms tumour is one of the most curable forms of cancer. More than 9 out of 10 children are cured completely.
Primary Sources
- Pritchard-Jones K, et al. SIOP Renal Tumour Study Group. Lancet. 2015.
- Brok J, et al. Management of Wilms' tumour. Eur J Cancer. 2017.
- Davidoff AM. Wilms tumor. Adv Pediatr. 2012.
Common Exam Questions
- Diagnosis: "Mass + Aniridia?"
- Answer: Wilms Tumour (WAGR syndrome).
- Comparison: "Wilms vs Neuroblastoma?"
- Answer: Wilms doesn't cross midline (usually) and child is well. Neuroblastoma crosses midline and child is surprisingly ill.
- Investigation: "First line imaging?"
- Answer: Abdominal Ultrasound.
- Pathology: "Biopsy needed?"
- Answer: NO (Risk of seeding).
Viva Points
- Aniridia: Why check? 30% of sporadic aniridia patients will develop Wilms. The PAX6 gene (eye) and WT1 gene (kidney) are neighbours on Chromosome 11p. A large deletion takes out both.
- Hypertension: Why? Renin secretion by the tumour or compression of the renal artery causing ischaemia of normal renal tissue (Goldblatt mechanism).
Medical Disclaimer: MedVellum content is for educational purposes and clinical reference. Clinical decisions should account for individual patient circumstances. Always consult appropriate specialists.