Nucleolar organizer regions in bladder cancer: application to urinary cytology

We investigated the relationship between the numbers of nucleolar organizer regions (NORs) in nonmalignant reactive cells and those in transitional cell carcinomas using urinary exfoliated cell specimens. Another aim of this study was to determine whether higher numbers of NORs are correlated with tumors with higher pathologic grade.

Nucleolar organizer regions, which are important for regulating protein synthesis, were counted by means of a silver staining technique in urinary exfoliated cells from 34 patients with transitional cell carcinoma (TCC) and in 30 patients with other urologic diseases (controls).

The number of argyrophilic proteins of the nucleolar organizer region (Ag-NORs) per cell (mean +/- SD) was 2.9 +/- 0.5 in the control group and 5.5 +/- 1.9 in patients with TCC, which was significantly higher than that in the controls (p < 0.001). It was 4.0 +/- 1.0 in patients with grade 1 TCC, 5.4 +/- 2.0 in those with grade 2 TCC, and 6.5 +/- 1.2 in those with grade 3 TCC. Although no statistically significant difference was observed between the groups, the patients with grade 2 TCCs with higher numbers of Ag-NORs showed a tendency to have more diffuse and/or invasive lesions.

This method is simple and quick, and can identify low-grade malignancy. It could be used as a tool for further grading of grade 2 TCCs and for determining prognosis.