Atypical cytologic and architectural features felt to be neoplastic that fall below the threshold for CIS.
Suffers from poor diagnostic reproducibility.
Nuclear abnormalities in the absence of inflammation, or disproportionate in the presence of inflammation, but not severe enough to merit CIS (image A) & (image B).
Usually normal urothelial thickness.
Mild loss of polarity and nuclear crowding.
Immunohistochemistry: may aberrantly express CK20 and have higher p53+.
On follow-up, 5-19% progress to bladder neoplasia including CIS.