Wilms tumor


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  • Clinical

    • mean age: 3-4 years
    • malignant, most common pediatric renal malignancy
    • syndromes
      • WAGR: Wilms, aniridia, genitourinary malformation, mental retardation, WT1 (11p13) deletion
      • Denys-Drash syndrome: mesangial sclerosis, pseudohermaphroditism, Wilms, WT1 point mutation
      • Beckwith-Wiederman syndrome: hemihypertrophy, macroglossia, omphalocele, visceromegaly, WT2 (11p15)
      • hemihypertrophy
      • familial nephroblastoma

  • Histology

    • border: pushing border
    • triphasic (may also be biphasic or monophasic)
      • blastemal cells: small round blue cells
      • epithelial: recapitulates nephrogenesis, tubules, papillary, primitive rosette-like structures. Can have heterologous mucinous or squamous epithelium.
      • stroma: skeletal muscle, fibroblasts, fat, cartilage, bone, ganglion, glia
    • patterns
      • diffuse blastemal: blastemal cells lack cohesiveness, invades adjacent connective tissue and vessels
      • nodular and sperpentine blastemal: nests and cords of blastemal cells in fibromyxoid stroma
      • diffuse anaplasia: ugly nuclei (more common in age > 5), abnormal mitotic figures.
      • focal anaplasia criteria
        • anaplasia is circumscribed
        • anaplasia is confined to renal parenchyma
        • anaplasia not in vascular spaces
        • the rest of the tumor lacks severe nuclear atypia
    • post-chemo changes
      • necrosis
      • xanthomatous histiocytic foci
      • hemosiderin
      • fibrosis
      • maturation of components (eg. striated muscle)

  • Stains

    • WT1 in immature elements, not sensitive or specific

  • Risk classification

    • low risk
      • cystic partially differentiated
      • completely necrotic (post-chemo)
    • intermediate risk
      • non-anaplastic types
      • only focal anaplasia
    • high risk
      • diffuse anaplasia
      • blastemal type (post-chemo)

  • Staging

    • I: completely resected (tumor within kidney)
    • II: completely resected (tumor infiltrating capsule, sinus vessels, beyond kidney)
    • III: residual tumor/positive margin
      • SIOP also counts necrotic nodes as stage III
    • IV: metastasis or positive lymph node
    • V: bilateral involvement at diagnosis. Sub-stage each side separately.
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