Abstract

For the identification of proliferating cells in tissue, the argyrophilic method for the demonstration of nucleolar organizer regions (Ag-NORs) have been described. To evaluate the applicability of Ag-NORs in surgical pathology, the authors have done Ag-NORs staining on 144 cases of routinely processed, formalin-fixed paraffin sections of various tissues; 15 normal tissues, 12 reactive and hyperplastic lesions, 30 benign neoplasms, 4 borderline lesions, and 83 malignant tumors. The results were summerized as follows; 1) In normal tissues, the mean numbers of Ag-NORs were highter in labile cells, especially in actively proliferating cells such as germ cells of testis, crypt epithelial cells in gastrointestinal mucosa, and lymphocytes from germinal center of tonsil and lymph node, than those of stable cells. 2) The mean numbers of Ag-NORs in reactive and hyperplastic lesions, benign neoplasms, and borderline lesions were similar to those of normal labile cells. 3) The mean numbers of Ag-NORs in carcinomas and sarcomas, (usually more than 2) significantly exceeded those of normal and non-malignant conditions. However, certain cases of carcinomas such as papillary carcinomas of thyroid, mucinous carcinoma of stomach, bronchioloalveolar carcinoma of lung, and adenoid cystic carcinoma of lung, and some of the leiomyosarcoma, malignant fibrous histiocytoma, and malignant schwannoma showed relatively lower numbers of Ag-NORs. 4) In non-Hodgkin's lymphomas, the high grade lymphomas showed more Ag-NORs than the low grade ones. From above results, it is suggested that the Ag-NORs technique is helpful in differentiation between malignant and non-malignant lesions. However, further evaluation on the significance of Ag-NORs upon the behavior of the cancer is to be made.

• Keywords: Ag-NORs;Nucleolar organizer regions;Argyrophilic staining;Proliferation activity