Nucleolar organizer regions distribution in fine needle aspiration cytological smears from breast lesions

Fine needle aspiration (FNA) cytology is now an integral part of the pre-operative investigation of breast lesions and the therapeutic protocol is today often planned on the basis of cytodiagnosis. However, from time to time the cytological picture may be equivocal or inconclusive. In recent years, nucleolar organizer region (NOR) scores have been explored for potential value in the diagnosis of malignancy as the scores in malignant nuclei are seen to be higher than in benign or reactive nuclei. With a view to applying NOR scoring in the evaluation of cytologically equivocal cases, we adopted the argyrophil technique for staining NOR s (AgNOR) in FNA cytological smears of 56 breast lesions, comprising 31 benign and 25 malignant lesions. Histological correlation was possible in 26 of these cases (17 malignant and 9 benign) and AgNOR scoring was done on paraffin sections of these as well. There was a significant difference between mean AgNOR scores in benign and malignant lesions in the cytological smears (P < 0.001). The AgNOR scores ranged from 2.5 to 5.0 per cell in benign lesions and 5.8 to 17.2 per cell in malignant lesions. None of the cases fell into the gray zone of overlap. One malignant lesion that was cytologically equivocal showed a mean AgNOR score of 6.08. The AgNOR scores on histological sections also showed a statistically significant difference (P < 0.001) between benign and malignant lesions with mean scores ranging from 1.34 to 2.58 dots per cell in benign lesions and scores of 2.42 to 5.28 dots per cell in malignant lesions. However, the scores overlapped in four cases and therefore it was considered unsuitable for routine diagnostic work. From this preliminary study, we conclude that an FNA AgNOR score of 5.0 and less strongly favours a benign lesion whereas a score above 5.0 would be in favour of a malignant lesion. A larger study would be needed to verify our impression that AgNOR scoring can be useful in cytologically equivocal cases.