Demonstration of the nucleolar organizer region by silver staining (AgNOR method) in research and in histopathological practice.

The silver-staining method for the detection of nucleolar organizer regions (AgNOR) was tested on a large material and the AgNORs evaluated in normal and pathological tissues, especially in various benign and malignant neoplasms. Pathological lesions were represented by dysplasias and in situ carcinoma of the uterine cervix, dysplasias and various histological forms of breast carcinoma, carcinomas of the lung, of urinary bladder, of prostate, various neoplasms of the gastrointestinal tract, trophoblastic disease, naevocellular naevi and melanomas of the skin, myeloproliferative diseases and haematological malignancies, and also by several cases of xenotransplanted human neoplasms in athymic nude mice. The AgNORs were evaluated using several procedures. Marked AgNOR heterogeneity in individual malignant tumours was found to be a common feature suggesting the presence of cellular subpopulations or clones with different proliferative activity and metabolic properties. Close correlation between the proliferative behaviour and the quantitative and qualitative change of AgNORs was found in most obviously malignant neoplasms. The method, however, could not recognize neoplastic cells as such and is therefore not a specific oncological marker. This limits the diagnostic contribution of the silver staining method in diagnostic pathology, where it does not exceed the value of routinely stained slides of good quality. In spite of these limitations, the AgNOR staining method seems to represent a valuable contribution in the study of some aspects of the proliferative lesions, such as their proliferative and metabolic activity, hormonal dependence etc.