Argyrophilic nucleolar organizer regions (AgNORs) are loops of ribosomal DNA in the nucleolus and are associated with acidic proteins that have a high affinity for silver.

In this study, the mean AgNOR counts were evaluated in specimens. Seventy three specimens were examined, including 16 normal thyroids, 19 nodular goiters, 21 follicular adenomas and 17 thyroid carcinomas (11 papillary, 4 follicular carcinomas, and 2 medullary carcinomas). The specimens were stained, using modified AgNOR staining method.

It has been shown that mean AgNOR count increases from normal thyroid (1.45 ± 0.21) to papillary carcinoma, nodular goiter (1.60 ± 0.29), thyroid carcinoma (total) (1.78 ± 0.38), follicular adenoma (1.79 ± 0.42), follicular carcinoma (2.10 ± 0.12) and medullary carcinoma (2.22 ± 0.32) (mean ± SD). But, statistical analysis of the above findings, using unpaired Student's t test showed that mean AgNOR counts in adenoma and carcinoma are significantly higher than normal thyroid (P< 0.05), but the difference between other groups was not significant.

There was also significant overlap in mean AgNOR counts of these groups. It can be concluded from these results that the mean AgNOR counts may have no diagnostic value in differentiating benign and malignant lesions of thyroid on paraffin embedded sections.