Focal versus diffuse anaplasia in Wilms tumor - New definitions with prognostic significance: A report from the National Wilms Tumor Study Group

Paulo Faria, J. Bruce Beckwith, Kiran Mishra, Craig Zuppan, Douglas A. Weeks, Norman Breslow, Daniel M. Green

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Anaplasia, defined by the presence of extreme nuclear and mitotic atypia, is a potent marker of adverse prognosis in Wilms tumor (WT). Anaplastic WT cells apparently have increased resistance to therapy rather than increased aggressiveness. The distribution of anaplasia should therefore have critical prognostic relevance. The original definitions for focal anaplasia (FA) and diffuse anaplasia (DA) were based on quantitative rather than topographical criteria and lacked prognostic significance. A new definition was developed based on the distribution of anaplastic changes within the tumor: FA applies only to tumors with anaplasia confined to one or a few discrete loci within the primary tumor, with no anaplasia or marked nuclear atypia elsewhere. This revised definition was evaluated in 165 cases with anaplastic WT entered on the third and fourth National Wilms Tumor Study. Only three relapses and one death occurred among 39 cases with FA, regardless of tumor stage, a result comparable to that for nonanaplastic WT. Eight children with metastases at diagnosis and FA in the primary tumor were alive and free of relapse; 22 of 23 children with stage IV DA WT died of tumor. This new definition reinforces the importance of carefully documenting the exact site from which each tumor section is obtained.

Original languageEnglish (US)
Pages (from-to)909-920
Number of pages12
JournalAmerican Journal of Surgical Pathology
Issue number8
StatePublished - Aug 1 1996



  • Anaplasia
  • Nephroblastoma
  • Ploidy
  • Prognostic marker
  • Resistance marker
  • Tumor stage
  • Wilms tumor

ASJC Scopus subject areas

  • Anatomy
  • Surgery
  • Pathology and Forensic Medicine

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