Silver-binding nucleolar organizer regions (AgNORs) in benign and malignant breast lesions: correlations with ploidy and growth phase by DNA flow cytometry.

Silver-binding nucleolar organizer regions (AgNORs) have been counted in sections of routinely processed paraffin-embedded tissue blocks and have been shown to assist in the distinction between benign and malignant lesions. We have examined 214 benign and malignant breast lesions by this method. The AgNOR counts were fibroadenomas 1.87 +/- 0.20 (mean +/- SD; n = 39), papillomas 1.92 +/- 0.21 (n = 28), sclerosing adenosis 1.96 +/- 0.24 (n = 23), epitheliosis 2.21 +/- 0.30 (n = 38), lobular carcinoma in situ 2.67 +/- 0.54 (n = 9), intraduct carcinoma 3.75 +/- 1.33 (n = 37), and invasive carcinoma 4.22 +/- 1.18 (n = 40). However, the counts in 25-30 per cent of epitheliosis lesions and intraduct carcinomas overlapped in the region of 2-3 AgNOR dots per nuclear profile. The AgNOR counts in carcinomas were also compared with ploidy and growth phase fractions (S + G2 + M%) by flow cytometry. Thirty-three of the 46 cancers with counts over 3 AgNOR dots per nuclear profile contained aneuploid cells (greater than 10 per cent of the total), whereas 8 of the 12 with counts below 3 comprised diploid cells only (P less than 0.05). Similar trends were noted with regard to growth phase fractions which were 19.15 per cent +/- 12.31 and 13.98 per cent +/- 5.55, respectively, for the two groups (P greater than 0.10). We conclude that this method alone does not offer a reliable histological discriminant for malignancy in the breast. However, AgNOR counting may provide information on breast cancer prognosis supplementary to that obtained from DNA flow cytometric analyses.