Nucleolar organizer regions in ovarian tumors: discrimination between carcinoma and borderline tumor.

Nonhistone nucleoproteins associated with the nucleolar organizer region (NOR) can be visualized by a silver-staining technique on paraffin-embedded tissues. The number of black dots (Ag NORs) appearing on the nuclei are thought to reflect cell differentiation of certain tumors and can be used as an adjunct in predicting their evolution. We applied this method to determine if Ag NORs counts could be used as a diagnostic aid in borderline tumors of the ovary. Thirty-two cases of adenocarcinomas, 25 cases of borderline tumors, and 14 cases of adenomas were selected from Bouin-fixed archival material after histological examination. Both mean values of Ag NORs counts demonstrated a progressive increase from adenomas to borderline tumors and to carcinomas; the differences were statistically significant. Using discriminant analysis, all cases of benign and malignant tumors except one adenoma and one carcinoma were discriminated as belonging to an individualized group. No difference was found between borderline tumor with peritoneal implants and those without peritoneal implants. The results indicate that the Ag NORs counting procedure may be useful in distinguishing borderline tumors from carcinomas and adenomas. Ag NORs counts cannot, however, predict the clinical behavior of borderline tumors of the ovary.