Diagnostic value of AgNOR method in thyroid cytopathology: correlation with morphometric measurements.

A silver staining technique was applied to 51 thyroid smears. The numbers of silver-stained nucleolar organizer regions (AgNORs) were counted, and the mean AgNOR and nuclear area per cell were determined with an image analyzer. The mean AgNOR count per cell was significantly higher in malignant than in benign lesions, but there was a considerable overlap. The mean AgNOR area and the mean SD of the AgNOR area per cell were significantly higher in carcinomas than in benign lesions (P = 10-9 and P = 5 x 10-10, respectively) and there were only two and one benign cases, respectively, of overlap. A strong correlation was observed between the mean AgNOR area and the mean nuclear area (r = 0.88), the former being a better discriminator between benign and malignant lesions. The AgNOR technique may contribute to routine thyroid cytopathology.