Comparison of the average value of nucleolar organizer regions in benign and malignant tumors of thyroid

The number of nucleolar organizer regions (NORs) can be used to determine the degree of cell activity or metabolism in histopathology specimens. The quantification of argylophilic nucleolar organizer regions (Ag NORs) was performed in 65 cases with benign and malignant thyroid tumors to determine whether Ag NOR count correlated with different histologic pattern pertinent to prognosis. Ag NORs were stained by a one-step silver method and examined in representive paraffin sections from 61 cases with malignant thyroid tumors and 4 cases with benign thyroid tumors. Primary tumors were surgically resectd and in each case AgNORs counts in the tumors were compared with their normal thyroid tissues as control groups. The mean AgNORs numbers per cell in tumoral tissue (benign and malignant) were 1.18±0.59. The mean AgNORs number per cell in malignant tumoral cells (2.69±0.58) was significantly (P<0.005) higher than benign thyroid tumor (2.08±0.46). The results of analysis of variance showed that mean AgNORs count in malignant thyroid tissue with their own normal thyroid tissue as control group, mean AgNORs count in benign thyroid tissue with their own normal thyroid tissue as control group, and mean AgNORs count in malignant thyroid tissues with benign thyroid tissues were significantly diffierent.