Immunohistochemical expression of CK20, p53, and Ki-67 as objective markers of urothelial dysplasia.

Urothelial dysplasia and carcinoma in situ (CIS) are related to recurrence and progression of urothelial carcinoma. Distinguishing CIS and dysplasia from reactive atypia is often difficult on the basis of histological features alone. Cytokeratin 20 (CK20), p53, and Ki-67 are related either to neoplastic change or prognosis in urothelial proliferations. The objective of the present study was to establish the immunohistochemical pattern of these three antibodies in urothelial dysplasia and CIS. Three groups of patients were evaluated: 40 nonneoplastic urothelial samples, 50 cases with histologically incontrovertible CIS, and 30 samples with nonconclusive atypical changes (atypia of unknown significance). Monoclonal antibodies (MoAb) against CK20, p53, and Ki-67 (MIB-1) were used on paraffin-embedded samples. Nonneoplastic urothelium showed no reactivity to CK20 except for umbrella cells; p53 and Ki-67 were negative or weakly positive in <10% of basal cells. In the CIS group, 42% showed positivity for all three MoAb; 44%, for two; and 14%, only for one. CK20 was positive through the full thickness of the urothelium in 72% of cases, p53 was positive in 80% of cases, and Ki-67, in 94% of cases. In the third group, the suspected dysplastic cells showed strong positivity in scattered cells through the epithelium in 75% of cases. Aberrant CK20 expression in urothelial cells plus overexpression of p53 and Ki-67 are indicators of dysplastic change in urothelial mucosa. Thus, immunohistochemistry is a useful tool to confirm the diagnosis of CIS and could be helpful to distinguish dysplastic changes from reactive atypia.