Stereological estimation of nucleolar organizer regions in prostatic tissue with an optical disector.

Silver-stained nucleolar organizer regions (AgNORs) were studied in 10 hyperplastic, 10 inflamed, nine prostatic intraepithelial neoplastic (PIN) and 20 malignant prostatic lesions. Optical disector measurement on 15 micron sections showed that upper frequency limits for 1.5 microns and 2.0 microns AgNOR particles were 10% and 2% in benign lesions and 18% and 9% in PIN. Using these cut-off values for diagnosis we found a low sensitivity and high specificity in distinguishing benign lesions from PIN and PIN from carcinoma. A high sensitivity and high specificity were obtained in separating benign lesions from carcinoma. AgNOR typing on routine "two-dimensional" sections showed that upper frequency limits for types B2, B3 and C2 were 25%, 3% and 0% in benign lesions and 38%, 23% and 11% in PIN. Using these cut-off values for diagnosis we found lower sensitivity and specificity values among all the differential diagnostic categories. We conclude that although both methods may contribute to the differential diagnosis between benign and malignant prostatic lesions, stereological estimation was a technically simple method, ensuring unbiased sampling and resulting in higher sensitivity and specificity. It may thus prove helpful in the differentiation of borderline cases in routine diagnostic pathology.