[AgNOR cytometry by means of automatic image analysis--a contribution to standardization]

The silver staining of nucleolar organizer regions (AgNORs) was evaluated in a total of 697 tumours from ten different tissues. By means of qualitative light microscopy, type, duration and delay of fixation proved to be influential in determining the AgNOR result. For standardization of the AgNOR technique, staining time series in 30 tissue blocks of the ten types of tissue were evaluated using digital image analysis. The silver incubation time which rendered the most distinct diagnostic difference in the AgNOR content of benign and malignant tissue varied considerably. Accordingly, staining time has to be adjusted to the individual argyrophilia of each tissue block or tissue section, for which the use of internal staining standards such as lymphocytes or connective tissue was found to be mandatory. For routine purposes, the appropriate silver incubation time is achieved if AgNORs are visible as black dots mainly within the nucleoli of proliferating cells.