Wilms Tumor in Children
Wilms Tumor in Pediatric Age
Wilms tumor, also known as nephroblastoma, is the most common renal malignancy in children. It typically affects children under the age of 5 and represents about 5% of all pediatric cancers. This embryonal tumor arises from nephrogenic rests, which are foci of metanephric blastema that persist beyond 36 weeks of gestation.
Key Points:
- Most common primary renal tumor in children
- Peak incidence between 2-5 years of age
- Originates from embryonic kidney cells
- Generally presents as an asymptomatic abdominal mass
- Treatment involves a multimodal approach: surgery, chemotherapy, and sometimes radiotherapy
Epidemiology
Wilms tumor accounts for approximately 95% of all kidney tumors in children. The incidence is about 1 in 10,000 children, with a slight female predominance.
Key Points:
- Incidence: 7-10 cases per million children under 15 years
- Median age at diagnosis: 3-4 years
- Bilateral in 5-10% of cases
- Associated syndromes: WAGR, Denys-Drash, Beckwith-Wiedemann
Pathogenesis
The development of Wilms tumor involves complex genetic and epigenetic alterations. Key genes implicated in its pathogenesis include:
- WT1 (Wilms Tumor 1) gene: Located on chromosome 11p13
- WT2 gene: Located on chromosome 11p15
- WTX gene: Located on the X chromosome
Mutations or deletions in these genes can lead to abnormal kidney development and tumor formation.
Clinical Presentation
The classic triad of Wilms tumor includes:
- Abdominal mass (most common presenting sign)
- Abdominal pain
- Hematuria
However, this triad is present in less than 10% of cases. Other symptoms may include:
- Hypertension (due to renin production by the tumor)
- Fever
- Malaise
- Anorexia
- Weight loss
Diagnosis
Diagnosis of Wilms tumor involves a combination of imaging studies and histopathological examination:
Imaging:
- Ultrasound: Initial imaging modality
- CT or MRI: For detailed tumor assessment and staging
- Chest X-ray or CT: To evaluate for lung metastases
Laboratory Studies:
- Complete blood count
- Renal and liver function tests
- Urinalysis
Biopsy:
Typically performed during initial surgical resection. In some cases, a percutaneous core needle biopsy may be done preoperatively.
Bilateral Wilms’ tumour with fullness of both flanks and the right renal mass is seen crossing the midline.(source)Staging
The National Wilms Tumor Study Group (NWTSG) staging system is commonly used:
- Stage I: Tumor limited to kidney, completely excised
- Stage II: Tumor extends beyond kidney but completely excised
- Stage III: Residual nonhematogenous tumor confined to abdomen
- Stage IV: Hematogenous metastases (lung, liver, bone, brain)
- Stage V: Bilateral renal involvement at diagnosis
Treatment
Treatment of Wilms tumor involves a multimodal approach:
Surgery:
- Radical nephrectomy: Primary treatment for unilateral tumors
- Nephron-sparing surgery: Considered for bilateral tumors or predisposing syndromes
Chemotherapy:
- Actinomycin D and Vincristine: Standard for favorable histology
- Doxorubicin added for higher stages or unfavorable histology
Radiotherapy:
- Used for higher stages (III and IV)
- Whole lung irradiation for lung metastases
Prognosis
The prognosis for Wilms tumor is generally favorable, with overall survival rates exceeding 90% for localized disease.
Prognostic Factors:
- Stage at diagnosis
- Histological subtype (favorable vs. unfavorable)
- Age at diagnosis (younger age generally has better prognosis)
- Tumor weight
- Response to chemotherapy
Long-term follow-up is essential due to potential late effects of treatment and the risk of second malignancies.
Wilms Tumor in Pediatric Age
- What is the most common renal tumor in children?
Wilms tumor (nephroblastoma) - What is the peak age of incidence for Wilms tumor?
3-4 years old - Which gene is most commonly mutated in Wilms tumor?
WT1 gene - What is the most common presenting symptom of Wilms tumor?
Painless abdominal mass - Which syndrome is associated with an increased risk of developing Wilms tumor?
WAGR syndrome - What is the standard imaging modality for diagnosing and staging Wilms tumor?
CT scan of abdomen and chest - Which histological finding is associated with poor prognosis in Wilms tumor?
Anaplasia - What is the overall survival rate for localized Wilms tumor?
>90% - Which chemotherapy drugs are commonly used in the treatment of Wilms tumor?
Vincristine and actinomycin D - What is the name of the staging system used for Wilms tumor?
Children's Oncology Group (COG) staging system - Which congenital anomaly is associated with an increased risk of Wilms tumor?
Aniridia - What is the typical surgical approach for unilateral Wilms tumor?
Radical nephrectomy - Which organ is the most common site of metastasis in Wilms tumor?
Lungs - What is the name of the precursor lesion of Wilms tumor?
Nephrogenic rests - Which syndrome is characterized by hemihypertrophy and an increased risk of Wilms tumor?
Beckwith-Wiedemann syndrome - What is the role of radiation therapy in the treatment of Wilms tumor?
Used for higher stage disease or unfavorable histology - Which tumor marker is elevated in some cases of Wilms tumor?
Alpha-fetoprotein (AFP) - What is the name of the bilateral Wilms tumor predisposition syndrome?
Denys-Drash syndrome - Which imaging finding is characteristic of Wilms tumor?
"Claw sign" on CT or ultrasound - What is the typical duration of chemotherapy for favorable histology Wilms tumor?
18-24 weeks - Which chromosomal region is commonly lost in Wilms tumor?
11p15 - What is the name of the cooperative group that conducts most Wilms tumor clinical trials?
Children's Oncology Group (COG) - Which histological feature is characteristic of favorable histology Wilms tumor?
Triphasic pattern (blastemal, stromal, and epithelial components) - What is the recommended follow-up imaging for Wilms tumor survivors?
Abdominal ultrasound - Which gene is associated with the development of rhabdoid tumors of the kidney?
SMARCB1 (INI1) - What is the name of the surgical approach that aims to spare renal tissue in bilateral Wilms tumor?
Nephron-sparing surgery - Which late effect is associated with abdominal radiation in Wilms tumor treatment?
Scoliosis - What is the name of the phenomenon where Wilms tumor extends into the renal vein or inferior vena cava?
Tumor thrombus - Which molecular pathway is targeted by newer treatments for relapsed Wilms tumor?
IGF1R/PI3K/mTOR pathway - What is the most common second malignancy in Wilms tumor survivors?
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