Assessment of proliferative activity of thyroid Hürthle cell tumors using PCNA, Ki-67 and AgNOR methods

We have undertaken an attempt to compare the application efficacy of the proliferative activity markers in differential diagnosis of thyroid Hürthle cell tumors (HCT) using the PCNA and Ki-67 labeling and AgNOR visualisation techniques. The present work is a retrospective analysis of 78 Hürthle cell tumors: 20 Hürthle cell carcinomas (HCC), 32 Hürthle cell adenomas (HCA) and 26 hyperplastic nodules with Hurthle cell metaplasia (HCM). Five microm sections were stained according to AgNOR technique and labeled with antibodies against PCNA and Ki-67. AgNOR dot count in the nucleus and proliferative index (PI - percentage of cells expressing PCNA and Ki-67) in randomly chosen nuclei (100 in case of AgNOR and over 1000 in case of PI) were evaluated in each slide. The mean values of AgNOR dot count, PI-PCNA and PI-Ki-67 in HCC, HCA and HCM were respectively: 5.1, 61.3 and 54.9; 3.4, 42.4 and 38.6 and 2.5, 39.3 and 34.3. Statistically significant difference was found in all the proliferative activity markers between malignant and benign tumors: HCC:HCA (p<0.01) and HCC:HCM (p<0.001). There was no statistically significant difference between HCA and HCM.