Nucleolar organizer regions of benign pathology of the parathyroids

: Nucleolar organizer regions (NOR) have DNA loops containing genes that encode for ribosomal RNA; some proteins located near the NORs are argyrophilic and by Ploton's one step method we could quantify the NORs in sections of paraffin embedded tissues. We have evaluated the number of intranuclear dots in 46 parathyroid glands from 18 parathyroidectomies. The glands were weighed and the stromal fat was evaluated by a point-counting method. AgNORs were counted in 100 cells from each gland. The mean count was 3.03 in six adenomas (A), 2.39 in six cases of primary hyperparathyroidism (PH) and 2.63 in six cases of secondary hyperparathyroidism (SH). Statistical analysis performed by Mann-Whitney U test showed that differences between A and PH groups were significant. The difference between A and SH was also significant. The residual parathyroid tissue surrounding the adenoma had a significantly lower AgNOR mean count than adenomatous cells. The AgNOR mean number can be useful in assessing normal or suppressed parathyroid tissue.