Silver-stained nucleolar organizer regions in the differentiation of prostatic hyperplasia, intraepithelial neoplasia, and adenocarcinoma.

Nucleolar organizer regions (NORs) are loops of chromosomal DNA that ultimately direct the development of the nucleolus. These NORs are associated with argyrophilic acidic nonhistone proteins which have allowed the demonstration of NORs by a simple silver stain. This staining technique has been used to examine the number of silver-stained NORs (AgNORs) in malignant and benign conditions, and, in general, AgNOR numbers are increased in malignant tissues when compared with normal or benign conditions. More recently, this technique has been applied to premalignant lesions with varying results. We applied this silver stain to prostate lesions where nucleolar features are of diagnostic importance. The stain was applied to ten cases of prostatic hyperplasia, ten cases each of prostatic intraepithelial neoplasia (PIN) grades 1 through 3, and ten cases each of low grade, intermediate grade, and high grade adenocarcinoma. The counting was performed by image analysis. A significant mean difference did exist between low grade and the two higher grades of adenocarcinoma. There was no significant difference in AgNOR counts per nucleus in hyperplasia, PIN, or adenocarcinoma or between the three grades of PIN. The AgNOR silver stain is not useful in the differentiation of hyperplasia, the three grades of PIN, and adenocarcinoma. Also because of overlap among the three grades of adenocarcinoma, it is not useful in the differentiation of these lesions.