A 6-year-old previously healthy boy presented to his pediatrician with abdominal fullness for one month. The child had no abdominal or gastrointestinal complaints. On examination, he had left-sided abdominal firmness. An ultrasound revealed a mass that appeared to originate from the kidney. He was referred to pediatric oncology. CT scan of the abdomen confirmed a large kidney mass with displacement of the structures within the left abdomen, most consistent with a Wilms tumor (Figure 213-1). Work-up for metastatic disease, including a chest CT was negative. The patient underwent nephrectomy (Figure 213-2). Pathology of the mass revealed Wilms tumor with favorable histology. The child received chemotherapy and has been tumor-free.

Renal cancer, including Wilms tumor, accounts for approximately 6.3 percent of cancer diagnosed in children under the age of 15 years and 4.4 percent of cancer diagnosed in children and young adults under the age of 20 years.¹ Treatment may include surgery, chemotherapy, and radiation. With multimodality therapy, long-term cure rates exceed 85 percent for children diagnosed with favorable histology, even in cases of higher stage disease.

Nephroblastoma.

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  Approximately 550 children and young adults under 20 years of age are diagnosed with renal tumors in the US each year and approximately 500 of these are Wilms tumor.¹

  
  
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  Wilms tumor accounts for approximately 95 percent of all renal cancers in children under 15 years of age.

  
  
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  Wilms tumor occurs most commonly in children under age 5 years, with the highest incidence in the first 2 years of life.¹

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  Wilms tumor is an embryonal malignancy of the kidney.

  
  
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  It is believed to develop in retained nephrogenic rests which are foci of persistent embryonal kidney cells. Although nephrogenic rests may be seen in approximately 1 percent of kidneys at birth, they usually regress or differentiate early in life.²

  
  
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  Persistent nephrogenic rests outside of the perinatal period are felt to be precancerous lesions.

  
  
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  The majority of cases of Wilms tumor occur in healthy children who do not have any identifiable risk factors.

  
  
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  Approximately 10 percent of cases of Wilms tumor are associated with congenital urinary tract anomalies and may be associated with an established phenotypic syndrome.

  
  
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  Associated urinary tract anomalies include cryptorchidism and hypospadias.

  
  
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  Associated syndromes may be divided into overgrowth syndromes and nonovergrowth syndromes.

  
  
  
  
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    Overgrowth syndromes include:

    
    
    
    
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      Beckwith-Wiedemann (Wilms tumor and other manifestations such as macrosomia, macroglossia, omphalocele, prominent eyes, ear creases, large kidneys, pancreatic hyperplasia, and hemihypertrophy).

      
      
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      Perlman syndrome (Wilms tumor, fetal gigantism, visceromegaly, unusual face, and bilateral renal hamartomas with nephroblastomatosis).

      
      
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      Isolated hemihypertrophy.

      
      
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      Sotos syndrome (cerebral gigantism).

      
      
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      Simpson-Golabi-Behemel syndrome (Wilms tumor, organomegaly, bulldog facies, congenital heart disease, and polydactyly).

    
    
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    Nonovergrowth syndromes include:

    
    
    
    
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      WAGR syndrome (Wilms tumor, aniridia, genitourinary anomalies, and mental retardation).

      
      
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      Isolated aniridia.

      
      
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      Denys-Drash syndrome (Wilms tumor, progressive renal disease, and male pseudohermaphroditism).

      
      
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      Li-Fraumeni syndrome (Familial Wilms tumor).

  
  
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  Approximately 1 to 3 percent of cases of Wilms tumor are familial and are usually inherited in a dominant pattern with incomplete penetrance.³

  
  
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  Several genes have been identified as involved in the pathogenesis of Wilms tumor for both the sporadic form and those involving inherited predispositions syndromes, including familial occurrences.

  
  
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  Genetic changes in inherited syndromes involve germline mutations. These mutations may be inherited or de novo.

  
  
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  In addition to mutations in tumor suppressor genes, epigenetic changes at several sites have been identified as involved in the development of Wilms.⁴