Argyrophilic nucleolar organizer regions in proliferative lesions of the thyroid gland

To analyze various argyrophilic nucleolar organizer regions (AgNOR) parameters in proliferative lesions of the thyroid gland and to determine to what extent these parameters are influenced by the type of lesion or malignancy.

AgNORs were studied by light microscopy with the help of a semiautomated image analysis system in the normal thyroid gland (n = 6), nodular hyperplasia (n = 12), thyroid hyperfunction (n = 6); follicular adenoma (n = 21), oxyphilic adenoma (n = 10), follicular carcinoma (n = 10), oxyphilic carcinoma (n = 9), papillary adenocarcinoma (n = 14), and giant (n = 6) and small cell anaplastic carcinoma (n = 4). The investigated parameters included the number and area of AgNOR dots, the number of separate AgNOR locations, the ratio of the AgNOR dot area to the nuclear area and the area of single AgNOR dots.

The number and area of AgNOR dots were low in all the lesions, with the exception of giant cell anaplastic carcinoma. The number of separate AgNOR locations was the lowest in oxyphilic cell tumors and medium in papillary adenocarcinoma, while in all other lesions and normal thyroid it had higher values. The ratio of AgNOR area to the nuclear area and the area of single dots were similar in proliferative lesions and normal thyroid. In all proliferative lesions and in normal thyroid, there was a significant positive correlation (P < or = .0001) between the area or number of AgNOR dots on the one hand and nuclear area on the other.

The results indicate that in thyroid proliferative lesions, AgNOR values, particularly the number of separate AgNOR locations, correlate with the type of lesion but not with malignancy. Very typical are single clusters of dots within nuclei in oxyphilic tumors, malignant and benign, and in papillary adenocarcinomas, more or less often accompanied by single dots.