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Nephrogenic Rests

Image A

Image B

  • Foci of persistent nephrogenic cells resembling developing kidney.
  • Encountered in up to 40% of patients with Wilms' tumor.
  • Almost all patients with bilateral Wilm's tumor will have nephrogenic rests.
  • Two types:
    • Perilobar rests
      • Located at periphery of renal lobes (image A) & (image B).
      • Well-defined smooth borders and show predominance of blastema.
      • Often are numerous or diffuse.
      • Present in approximately 1% of infants < 3 months of age.

Image C

Image D

    • Intralobar rests
      • Located within renal lobe (cortical or medullary) (image C) & (image D).
      • Have more "infiltrative" borders and show predominance of stroma.
      • Usually are single.
      • Almost never seen EXCEPT with a Wilms' tumor.
  • Nephroblastomatosis: diffuse/multifocal nephrogenic rests, or multicentric/bilateral Wilms' tumors.
  • Indicates a greater probability of synchronous or metachronous bilaterality in a patient with Wilms' tumor.