Nucleolar organizer regions are DNA loops encoding rihbosomal RNA production and detectable by the argyrophilia of their associated proteins(AgNORs). AgNOR numbers correlate with cellular proliferating activity. Many studies have shown a significnt difference in AgNOR counts between benign and malignant tumors. AgNOR counts were also helpful in differential diagnosis. For the evaluation of its diagnostic utility in gastric lesions, a silver staining technique was carried out in paraffin sections of 5 control cases, 5 benign peptic ulcers, 7 hyperplastic polyps, 10 tubular adenomas, 16 early gastric adenocarcinomas and 15 advanced gastric adenocarcinomas. The results were as follows. The mean numbers of AgNORs in early and advanced gastric adenocarcinomas(1.94 and 2.16) were significantly higher than those of normal foveolar epithelium(1.43) and epithelia of benign gastric ulcers(1.54), hyperplastic polyps(1.64) and tubular adenomas(1.79). In malignancy, there was increased variability in size and shape of AgNORs.
There was little differences in mean AgNOR numbers between early and advanced gastric adenocarcinomas. Differentiation of the tumor made no difference in AgNOR numbers. From the above results, the AgNORs count, if its morphologic change are taken into consideration, is helpful in differentiation between malignant and non-malignant lesions.
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.