American Urological Association - Simple Cortical Cyst
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Simple Cortical Cyst

Image A

Image B

  • Most common cystic lesion of the kidney.
  • Sporadic and mostly clinically inconsequential.
  • Mostly seen incidentally in radiology or in autopsy.
  • Clinical: Rare before age of 40; increase with age thereafter.
  • Gross:
    • May be multiple and large in older patients; otherwise, solitary simple cysts (as the name implies!) (image A).
    • Unilocular cyst with smooth lining and contain clear fluid.
  • Histology:
    • Cyst lined by a flattened or attenuated layer of cells (image B), or may lack an epithelial lining (denuded).
    • May be surrounded by fibrosis.
  • DDX:
    • Cystic nephroma/mixed epithelial and stromal tumor: Cysts with hobnailed cells + cellular stroma ("ovarian type stroma").
    • Cystic RCC: Multilocular cyst or partially cystic and lined by clear cells.