By using a silver staining technique, nucleolar organizer regions associated protein (Ag-NORs) ha ve been studied in paraffin sections of oral squamous cell carcinomas, benign lesions, such as leukoplakia and papilloma, and normal oral mucosa.The mean numbers of Ag-NORs were: squamous cell carcinoma (n=19), 6.18±1.84;papilloma (n=9), 2.70±0.50; leukoplakia (n=10), 2.92±0.69;normal oral mucosa (n=4), 2.48±0.13.There was a significant difference in the mean number of Ag-NORs between squamous cell carcinoma and the other two groups (P>0.05).The number of Ag-NORs seemed to have relations to the cellular atypism of squamous cell carcinoma and the grade of epithelial dysplasia of leukoplakia.These findings suggest that quantification of Ag-NORs may be used for differential diagnosis of malignant and benign oral tumors, and estimation of proliferative activity of oral preneoplastic and neoplastic lesions.
