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Nucleolar organizer regions in follicular tumors of the thyroid
Y Shem-Tov1, M Straus, Y P Talmi
1Department of Otolaryngology, Hasharon Hospital, Golda Medical Center, Petah-Tiqva, Israel.
Background:
Nucleolar organizer regions (NORs) are loops of ribosomal DNA that occur in nucleoli and that transcribe to ribosomal RNA. NORs have been identified by means of the Ag-NOR technique in routinely processed tissues, and were found to be of discriminative value between some types of benign and malignant lesions.
Methods:
Follicular lesions of the thyroid (17 adenomas and 25 carcinomas) were examined. Ten normal thyroids served as the control group. All slides were stained by the Ag-NOR technique and the number of Ag-NOR dots were counted in 50 randomly selected cells. The mean number of Ag-NORs was calculated for each case. Data were statistically analyzed by the Student's unpaired t test.
Results:
The mean Ag-NOR counts were statistically higher in follicular carcinomas as compared to either follicular adenomas or the normal thyroid. Higher Ag-NOR counts were found in the more aggressively behaving tumors.
Conclusions:
It is suggested that the Ag-NOR technique could be of use as an adjunct to diagnostic histopathology and as an indicator of biologic behavior in follicular tumors of the thyroid.