Immunohistochemical Differentiation between Urothelial Papillomas and Papillary Neoplasms of Low Malignant Potential of the Urinary Bladder

Background: Urothelial papilloma and non-invasive papillary carcinoma are common neoplasms of the urinary bladder. Distinguishing papillomas and papillary carcinomas, especially the low grade type, is often debatable on the basis of histological features alone. Materials and Methods: We investigated immunohistochemical expression of cytokeratin 20 (CK20), p53, and Ki-67 in a group of 20 urothelial papilloma cases and 30 noninvasive papillary neoplasms of low malignant potential (PNLMP) of the urinary bladder. Whole tissue sections were examined. Results: Among the 30 carcinoma cases, 12 (40%) showed strong reactivity for the whole panel, 16 (53%) reacted positively for two markers, and 2 (7%) reacted just to one of them. Ki-67 was considered positive in 27 cases (90%) and p53 in 24 (80%), CK20 showed positive reactivity in 21 cases (70%). Only small percentages of papillomas were positive, and then only weakly. Conclusions: We concluded that the intense positivity of suspicious cells for at least one of these markers would confirm the presence of malignant changes and favours the diagnosis of carcinoma.