Wilms Tumor (Nephroblastoma): Symptoms, Causes, Diagnosis, and Treatment
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Overview
Wilms tumor, also called nephroblastoma, is the most common kidney cancer in children. It typically appears in children under 5 years of age, usually in one kidney (unilateral) but can affect both (bilateral) in a minority of cases. With today’s coordinated care—surgery, chemotherapy, and when needed radiotherapy—most children can be treated successfully.
At MedicalPoint Hospital, our pediatric oncology, pediatric urology, radiology, radiation oncology, pathology, genetics, and supportive-care teams work together to provide evidence-based, family-centered treatment guided by international protocols (e.g., COG/SIOP).
What is Wilms Tumor?
Wilms tumor is a malignant (cancerous) tumor of the kidney that arises from immature kidney cells. It is different from adult kidney cancers in both biology and treatment. Disease behavior can vary from favorable histology (more common, better prognosis) to anaplastic types (rarer, more aggressive). Although it usually begins in one kidney, it may rarely involve both kidneys (bilateral disease) at diagnosis.
Where can it spread? The most common sites are nearby lymph nodes and the lungs; spread to the liver can occur less often. Metastases to bone, bone marrow, or brain are uncommon in initial presentation.
Why does Wilms Tumor occur?
There is no single cause. Research shows a role for embryologic (developmental) genetic changes during kidney formation:
- Inactivating or altered genes such as WT1, WTX (AMER1), and CTNNB1 (β-catenin) are found in a subset of tumors.
- Additional genes occasionally implicated include TP53 (more often in anaplastic tumors) and MYCN.
- Some children inherit a predisposition as part of genetic syndromes; others have non-inherited (somatic) mutations only in tumor cells.
Syndromes associated with higher risk
Children with the following conditions warrant genetics consultation and structured surveillance:
- WAGR syndrome: Wilms tumor, Aniridia (absence of the iris), Genitourinary anomalies, and Range of neurodevelopmental differences (usually involves WT1 region).
- Denys–Drash syndrome: early kidney disease (nephrotic syndrome) and genital differences in genetic males; high Wilms risk.
- Beckwith–Wiedemann spectrum: prenatal/postnatal overgrowth, enlarged tongue (macroglossia), abdominal wall defects; elevated risk of Wilms and some liver tumors.
- Other rarer associations: Frasier, Sotos, Perlman, Li-Fraumeni, Simpson–Golabi–Behmel, and trisomy 18 (Edwards).
Tip for families: If your child has a known predisposition syndrome or multiple congenital features, ask about renal ultrasound surveillance during early childhood.
Signs and symptoms
Many children appear well, and a parent may first notice a painless abdominal mass. Common features include:
- Abdominal swelling or a firm lump
- Abdominal pain or discomfort
- Blood in the urine (hematuria)
- High blood pressure (hypertension) or occasionally low blood pressure during complications
- Fever, fatigue, loss of appetite, or anemia
- Urinary tract infections (less common as a primary clue)
- If disease has reached the lungs: shortness of breath or cough
Seek urgent medical care if a new abdominal mass is felt, if urine turns red/brown, or if breathing difficulties occur.
How is Wilms Tumor staged?
Staging describes the extent of disease and guides therapy. Modern systems (Children’s Oncology Group [COG] in North America; SIOP in Europe/elsewhere) are broadly similar:
- Stage I: Tumor confined to the kidney and completely removed by surgery; renal capsule intact.
- Stage II: Tumor extends beyond the kidney (e.g., into fat or vessels) but can still be completely removed.
- Stage III: Residual tumor remains in the abdomen after surgery or there is lymph-node involvement; not fully removable without risk.
- Stage IV: Distant spread (most commonly lungs, also liver or other organs).
- Stage V: Tumors present in both kidneys at diagnosis; each side is staged separately.
Relapse (recurrence) can occur locally in the abdomen or at distant sites (often lung). Refractory disease refers to tumors that do not shrink adequately with initial therapy.
How is Wilms Tumor diagnosed?
Diagnosis uses a combination of history, examination, imaging, and pathology, always balancing accuracy with safety to avoid tumor rupture.
Initial tests
- Ultrasound of the kidneys (no radiation) to define a renal mass.
- Contrast-enhanced CT or MRI of abdomen/pelvis for surgical planning and assessment of vessels and lymph nodes.
- Chest imaging (X-ray and/or CT) to look for pulmonary metastases.
- Laboratory tests: complete blood count (for anemia), kidney and liver function, coagulation profile, and urine analysis.
Tissue diagnosis
- Under COG protocols, many unilateral renal masses suspected to be Wilms undergo primary nephrectomy (surgical removal) with surgical lymph-node sampling; the pathology then confirms diagnosis and stage.
- Under SIOP protocols, children typically receive pre-operative chemotherapy to shrink the mass and lower rupture risk, followed by surgery and pathology-based risk assignment.
- Routine needle biopsy is not performed in typical unilateral cases because it can alter stage (and therefore intensify treatment). Biopsy may be considered when the diagnosis is uncertain or in bilateral disease to guide kidney-sparing strategies.
At MedicalPoint Hospital, we tailor the pathway to the child—using either “up-front surgery” or “pre-op chemo” strategies according to international guidance, imaging features, and surgical feasibility.
Treatment options (personalized and protocol-driven)
Therapy depends on stage, tumor histology, genetic features, age, and whether one or both kidneys are involved. Care is delivered by a multidisciplinary pediatric oncology team.
1) Surgery
- Radical nephrectomy (removal of the affected kidney and tumor) with lymph-node sampling is standard for most unilateral tumors.
- Nephron-sparing (partial) nephrectomy may be used in selected cases (e.g., bilateral tumors, solitary kidney, or when preserving kidney function is critical).
- Surgeons take special precautions to avoid tumor rupture, which can upstage disease.
2) Chemotherapy
Most children receive multi-agent chemotherapy. Common drugs include:
- Vincristine
- Dactinomycin (actinomycin D)
- Doxorubicin (added for higher-stage or higher-risk disease)
Regimens and duration vary by stage and histology. Side effects can include low blood counts, hair loss, nausea, neuropathy, and—less commonly—heart or hearing effects; children are closely monitored, and supportive care is provided.
3) Radiotherapy
Used selectively, for example:
- Stage III abdominal disease after surgery
- Pulmonary metastases that do not fully clear with chemotherapy
- Some anaplastic or unfavorable-risk tumors
Modern planning aims to minimize dose to growing tissues while maintaining tumor control.
4) Bilateral disease (Stage V)
Goals include curing the cancer and preserving kidney function:
- Often begin with neoadjuvant chemotherapy to shrink tumors
- Plan kidney-sparing surgery on both sides when feasible
- Dialysis or transplant is rarely needed at diagnosis but may be considered if significant kidney function is lost
5) Relapsed or refractory Wilms tumor
Care is individualized and may include different chemotherapy combinations, surgery for residual lesions, targeted radiation, and participation in clinical trials when appropriate.
Living through and after treatment
- Follow-up schedule: regular visits with physical exam, blood pressure checks, kidney function tests, and imaging as indicated.
- Late effects monitoring: potential impacts on heart, hearing, growth, fertility, and second cancer risk are assessed based on drugs and radiation received.
- Family support: nutrition, psychosocial services, school re-integration, and vaccination guidance are part of comprehensive survivorship care at MedicalPoint.
When to call the care team urgently
- Fever or signs of infection during chemotherapy (neutropenia risk)
- Uncontrolled pain, new abdominal swelling, shortness of breath, or blood in urine
- Severe vomiting, dehydration, or decreased urine output
MedicalPoint Hospital’s approach
- Multidisciplinary tumor board reviews every case.
- Pediatric surgeons skilled in nephron-sparing techniques when appropriate.
- Onsite pediatric anesthesiology, interventional radiology, and genetics counseling.
- Evidence-based protocols aligned with COG/SIOP and adapted to the child’s needs.
- Family-centered support: play therapy, nutrition, psychology, and social services.
Plain-language glossary
- Nephrectomy: surgery to remove the kidney.
- Histology: how tumor cells look under the microscope and how aggressive they are.
- Metastasis: spread of cancer to other organs.
- Anaplasia: unfavorable microscopic appearance indicating more aggressive behavior.
References & further reading
- National Cancer Institute (NCI) PDQ®: Wilms Tumor and Other Childhood Kidney Tumors—Patient/Health Professional Versions.
- American Cancer Society: Wilms Tumor (Nephroblastoma) in Children.
- Children’s Oncology Group (COG) Family Handbooks and clinical guidance.
- International Society of Paediatric Oncology (SIOP) renal tumor protocols and parent resources.
This article provides general information and does not replace medical advice. For a child with a kidney mass or suspected Wilms tumor, please contact a pediatric oncology center. MedicalPoint Hospital accepts referrals and offers second opinions.
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