Nucleolar organiser regions in hyperplastic and neoplastic prostatic tissue.

Silver-stained nucleolar organiser regions (AgNORs) were studied in 10 hyperplastic, 5 intra-epithelial neoplastic and 30 malignant prostatic lesions. Total AgNOR counts and types were compared with histological features. The total AgNOR count per nucleus was significantly higher (P less than 0.05) in prostatic intra-epithelial neoplasia (PIN) and adenocarcinoma compared with prostatic hyperplasia. In addition, satellite AgNORs predominated in hyperplasia, while medium-sized and large nucleoli with granular AgNORs were only observed in PIN and adenocarcinoma. The results indicate that, despite statistically significant differences, AgNOR counts are of no use for diagnosis of any single case in the groups studied, because of considerable overlap. AgNOR typing, however, may contribute to the differential diagnosis between benign and malignant lesions. We propose a new AgNOR typing system.