CD44 + p53 + CK20 can be used to
differentiate urothelial reactive atypia from CIS (carcinoma in situ) in
bladders. In normal urothelium, superficial umbrella cell layer shows reactivity
for CK20 only, whereas CD44 staining is limited to the basal and parabasal
urothelial cells and p53 nuclear staining is absent to focal. For urothelium
with reactive atypia, particularly in cases with marked atypia, CD44 shows
increased reactivity in all layers of the urothelium and is often absent in
neoplastic cells. CK20 and p53 staining remain identical to those seen in normal
urothelium. In cases of CIS, diffuse, strong cytoplasmic reactivity for CK20 and
diffuse nuclear reactivity for p53 is observed throughout the
urothelium.