Fine needle aspiration cytology combined with argyrophilic nucleolar organizer regions (AgNORs) in diagnosis of thyroid neoplasms.

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.