Bladder, ureter & renal pelvis

Other nonneoplastic

Flat lesions with reactive changes

Last author update: 1 June 2016
Last staff update: 1 November 2021

Copyright: 2003-2023,, Inc.

PubMed Search: Flat lesions with reactive changes

Monika Roychowdhury, M.D.
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Cite this page: Roychowdhury M Flat lesions with reactive changes. website. Accessed September 25th, 2023.
Definition / general
  • Inflammatory atypia characterized by mild nuclear abnormalities in acutely or chronically inflamed urothelium
  • Uniformly enlarged and vesicular nuclei, central prominent nucleoli
  • May have frequent mitotic figures involving the lower layers of urothelium
Clinical features
  • May have history of cystitis, infection, instrumentation, stones or therapy
  • Not neoplastic but may coexist with dysplasia or carcinoma in situ
  • Most patients present with hematuria or irritative symptoms (frequency, urgency, dysuria)
Prognostic factors
Gross description
  • Erythematous or inflamed urothelium cystoscopically
Microscopic (histologic) description
  • Urothelium is normal to slightly thickened and shows morphologic evidence of maturation
  • Cells have abundant cytoplasm, nuclei may be enlarged and may have prominent nucleoli
  • Lamina propria is usually inflamed with inflammation extending to the mucosa
  • No nuclear hyperchromasia, no pleomorphism, no coarse chromatin pattern
Positive stains
  • CK20 (limited to umbrella cells), CD44 (stains all cell layers)
Negative stains
Differential diagnosis
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