Evaluation of nucleolar organizer regions in human bladder cancers by light- and electron-microscopic morphometry

The number of nucleolar organizer regions (NOR) of human bladder cancers was evaluated at the light- and electron-microscopic level. The average number of argyrophilic NOR (AgNOR), stained by the one-step silver colloid method, was measured in benign and malignant urothelial cells in the human urinary bladder using a light microscope. The average number of nucleolar fibrillar centers (FC) per nucleus was also calculated by quantitative ultrastructural morphometry in the specimens from the same patients. Statistical evaluations revealed that the average number of AgNOR per nucleus was significantly correlated with the elevation of tumor grade and stage (p < 0.05). An average FC number per nucleus also increased in association with tumor grade and stage (p < 0.05). Although the average number of FC was 5.6 times higher than that of AgNOR, the correlation between the average number of FC and AgNOR was statistically significant. In conclusion, these results suggested that the silver staining method was a useful and convenient tool for the evaluation of the differentiation and invasive potential of bladder cancer cells at the light-microscopic level.