WHO / ISUP classification
Flat lesions with atypia

Author: Sean Williamson, M.D. (see Authors page)

Revised: 11 September 2017, last major update June 2012

Copyright: (c) 2002-2017, PathologyOutlines.com, Inc.

PubMed Search: Flat lesions with atypia [title]

Table of Contents
Definition / general
Cite this page: Williamson, S. Flat lesions with atypia. PathologyOutlines.com website. http://www.pathologyoutlines.com/topic/uretersflatlesions.html. Accessed July 21st, 2018.
Definition / general
  • Reactive atypia:
    • Inflammatory atypia
    • Uniformly enlarged and vesicular nuclei; central prominent nucleoli; may have frequent mitotic figures
    • May have history of instrumentation, stones or therapy
    • Not neoplastic
  • Atypia (flat) of unknown significance:
    • Between reactive atypia and dysplasia, more pleomorphism and hyperchromasia than expected for the amount of inflammation present
    • Should have close follow up and re-evaluation after inflammation subsides
    • In the bladder, some authors have recommend combining this category with reactive atypia since it is not clearly associated with adverse consequences