Correlation of two AgNOR counts with Ki‐67 labeling index: A study in fine‐needle aspirates of lymphoproliferative disorders and breast carcinoma

The Ki‐67 antibody binds to nonresting cells where Ki‐67 labeling index (KLI) reflects proliferative activity (PA). The argyrophilic nucleolar organizer regions (AgNOR) counts have been correlated to ploidy and/or PA. Two AgNOR counting methods distinguish ploidy from PA. The first count is the mean AgNOR count (mAgNOR) which correlates with ploidy. The second is the percentage of nuclei with ≥ 5 AgNORs/nucleus (pAgNOR) which reflects PA. To explore this relationship, we separately stained smears of 20 fine‐needle aspirates (FNAs) of lymphoproliferative disorders (n = 12) and breast carcinomas (n = 8) for AgNOR and Ki‐67. We also double‐stained 10 of the smears for both AgNOR and Ki‐67. The correlation of pAgNOR counts and KLI was statistically significant (P < 0.0001) whereas it was not between mAgNOR and KLI (P = 0.13). Additionally, using the double stain, the Ki‐67 negative cells had an AgNOR granule range of 1‐3/ nucleus with a mean of 1.33 (± 1.86 SD). The Ki‐67 positive cells showed an AgNOR granule range of 2‐12/nucleus with a mean of 4.15 (± 1.02 SD) (P < 0.0002). We thus conclude that pAgNOR is a more reliable indicator of PA than mAgNOR and that four AgNORs/nucleus is an acceptable number differentiating proliferating from resting cells. © 1994 Wiley‐Liss, Inc.