Pediatric renal tumors and masses

Pediatric renal tumors and masses are another group of diseases (just like cystic renal diseases in both the adult and child) that are bewildering in their number, nomenclature and overlapping findings.

Commoner lesions

• Wilms tumor: common in older children 1-8 years old
• nephroblastomatosis: congenital condition with persistent metanephric blastema in the kidneys of infants and children , with potential for malignant degeneration to Wilms tumor
• mesoblastic nephroma
  • most common neonatal renal mass; benign hamartoma but is nonetheless resected as sarcomatous degeneration is a concern
  • local invasion of perinephric tissues is also seen; when diagnosed and treated before 3 months of age prognosis is good

Adjacent to kidney

• neuroblastoma: not a tumor of the kidney, but of the adrenal and other neural crest tissues, it needs to be differentiated from a Wilms tumor, distinguishing features include
  • calcification more common (90% vs 15%)
  • encases vascular structures but does not invade them
  • younger age group (<2 years of age)
  • usually bilateral
  • poorly marginated
  • more common to have extension into chest
  • see distinguishing between neuroblastoma and Wilms tumor

Other tumors

• renal cell carcinoma: rare in the first two decades of life
• rhabdoid tumor
• clear cell sarcoma 
• ossifying renal tumor of infancy: rare and benign
• metanephric adenoma (embryonal adenoma)
• renal angiomyolipoma
• renal medullary carcinoma
• lymphoma

Other cystic masses

• pediatric cystic nephroma
• cystic partially differentiated nephroblastoma
• multicystic dysplastic kidneys (MCDK)
• medullary cystic disease complex