CK20 and CK5/6 Immunohistochemical Staining of Urothelial Neoplasms: A Perspective

Figure 9

(a) Cartoon depicting immunohistochemical staining pattern in a low-grade papillary urothelial carcinoma with CK20 expression limited to the umbrella cells and presence of a well-defined basal layer which expresses CK5/6. (b) High-grade urothelial carcinoma reveals expression of CK20 in all layers of urothelium except for the basal layer which contains CK5/6. This may represent an intermediate stage of dedifferentiation of the tumor. (c) In high-grade urothelial carcinoma, the basal layer may be absent but the diffuse CK20 pattern of staining is maintained. These features may indicate further dedifferentiation of the carcinoma.