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NORs are the loops of DNA that contain the sites of ribosomal genes around which the nucleolus is formed during telophase of mitosis. In light microscopy they can be visualized by simple silver staining technique as small dark dots within the nucleus. It has been recognized that in many neoplasms, especially malignant AgNORs are more numerous and often atypical when compared with benign tumors and normal tissue. We have introduced this novel technique to the fine needle cytology of thyroid neoplasms (n = 56). We have analyzed the number, the area of AgNORs, the number of clustered AgNORs in the nucleus and the ratio of AgNOR area to the nuclear area and the area of single AgNOR by means of semiautomatic computerized image analysis. We have studied cytological samples consisting of 7 simple goiters, 7 hyperplasias, 15 follicular adenomas, 7 oxyphilic follicular adenomas, 6 follicular carcinomas, 8 oxyphilic follicular carcinomas, 6 papillary adenocarcinomas. In this study we have demonstrated that some differences in the AgNORs value are associated with the type of tumor rather than with malignancy. Location of the AgNORs seems to be very typical for some types of tumors. For example in oxyphilic neoplasms they form single clusters in the nucleus and in papillary adenocarcinomas they form at least two abundant clusters. In other proliferative lesions of the thyroid gland location of AgNORs is less typical.

Among the patients directed to the Department of Endocrinology of the Institute of Internal Medicine for diagnostic examinations of the thyroid, 726 (647 women and 79 men, of age between 16 and 79 years) were qualified to surgery after scintigraphic detection of cold nodules. From this group, 474 patients had thin-needle biopsy specimens taken for cytologic examination. The results of the latter examinations have been compared with those of histologic examination performed on the tissue removed during surgery. The occurrence of a malignant tumor (in 99.1%--thyroid cancer) was found in 108 patients (22.8%) from the group having thin-needle biopsy performed. Comparison of the results of cytologic examination with those of postoperative histologic examination demonstrated low sensitivity of biopsy examination (50.0%), as opposed to high specificity (96.2%) and high accuracy (85, 3%). Analysis of the false-negative results (54/108) revealed that the main causes of errors are difficulties in differentiation of adenoma from follicular carcinoma. Widening of the indications to surgery by a group of patients with adenoma will increase sensitivity to 84.8% and will require including into the operated group of about 50% of patients with scintigraphically diagnosed cold nodules: The introduction of the new term: "urgent strumectomy", has been proposed; also a diagnostic algorithm, useful for early diagnosis of malignant tumors of the thyroid, has been discussed.