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- Most common renal tumor in children; fifth most common pediatric malignancy
- An embryonal renal neoplasm containing blastemal, stromal, or epithelial cell types, usually affecting children <5 years of age
- Staging: In the United States, National Wilms Tumor Study (NWTS) group staging is done pretreatment based on radiographic imaging and surgery, whereas in Europe/Asia, Société Internationale d’Oncologie Pédiatrique (SIOP) staging is done after neoadjuvant chemotherapy is administered (1):
- I: tumor limited to kidney; completely excised
- II: tumor extends beyond kidney; completely excised
- III: residual nonhematogenous tumor confined to abdomen (lymph nodes positive, spillage of tumor, peritoneal implants, extension beyond resection region)
- IV: hematogenous metastases
- V: bilateral renal involvement
- System(s) affected: renal/urologic
- Synonym(s): nephroblastoma
- Occurs only in children
- Most common renal malignancy in childhood
- Frequency rare in East Asian populations than whites
- Frequency higher in black children than in whites
- Predominant age: median age of 36.5 months
- Predominant sex: female > male (1.1:1)
- Represents 6–7% of all childhood cancers
- >80% are diagnosed before 5 years of age (median age is 3.5 years at diagnosis).
- Wilms tumor makes up 95% of all renal cancers in children <15 years (2).
United States: 0.69/100,000; 7.6 cases/1 million children <15 years old
Etiology and Pathophysiology
- Hereditary or sporadic forms of genetic mutation
- Familial form: autosomal dominant trait with incomplete penetrance (1%)
- Potential of parental occupational exposure (machinists, welders, motor vehicle mechanics, auto body repairmen)
- Several congenital anomalies are known to be associated with Wilms tumor. A two-stage mutational model has been proposed: occurrence in either hereditary form or sporadic form. Patients with aniridia have a deletion of the short arm of chromosome 11 (11p13).
- Abnormalities of chromosome 11 at the 11p15 locus are associated with Beckwith-Wiedemann syndrome. Wilms tumor-suppressor gene (WT1) has been identified as well as additional candidates for another suppressor gene (WT2). Chromosome band 17q12–17q21 has been linked to two kindreds with Wilms tumor, and other kindred are associated with a Wilms tumor predisposition gene at 19q13.3–19q13.4. Loss of heterozygosity at chromosomes 16q and 1p is associated with adverse outcome (1).
- p53 is associated with anaplastic Wilms tumors (2).
- Familial occurrence (5%) (2)
- These patients tend to have earlier age of onset.
- Familial patients have greater risk of bilateral disease.
- Parental occupation (machinists, welders, motor vehicle mechanics, auto body repairmen)
- Maternal exposure to pesticides prior to child’s birth (3)
- High birth weight or preterm birth (3)
- Compared with firstborn, being a second or later birth may be associated with significantly decreased risk of Wilms tumor (3).
- Routine surveillance in patients with syndromes associated with Wilms tumor
- Routine screening with serial renal US at 3- to 4-month intervals has been recommended in children who have syndromes associated with an incidence of Wilms tumor >5% (4)[C].
- Routine screening with serial renal US is also recommended for infants born to kindreds with familial Wilms (every 3 to 4 months until age 7 years) (4)[C].
Commonly Associated Conditions
- Aniridia (partial or complete absence of iris) 600 times normal risk
- Hemihypertrophy (100 times normal risk)
- Duplicated renal collecting systems
- Denys-Drash syndrome (nephropathy, renal failure, male pseudohermaphroditism, Wilms tumor)
- Klippel-Trenaunay syndrome
- Wilms tumor, aniridia, genitourinary malformations, and mental retardation (WAGR) complex
- Beckwith-Wiedemann syndrome (visceromegaly, macroglossia, omphalocele, hyperinsulinemic hypoglycemia)