Application of argyrophilic nucleolar organizer region (AgNOR) staining for cytology of biliary tract carcinomas

Purpose/Background Increased numbers of argyrophilic nucleolar organizer region (AgNOR) dots reflect higher proliferating activity of malignant cells. Methods To determine whether AgNOR staining is suitable for cytology of bile in biliary diseases as an ancillary diagnostic method, we examined the mean number of AgNOR dots (MNA) in cells of both bile smear and tissue sections in 14 benign biliary diseases and 25 malignancies of the biliary tract. The malignant diseases consisted of 11 gallbladder cancers, 10 bile duct cancers, and 4 ampulla cancers in patients who underwent surgical resection. Results of AgNOR staining were available in 15 min, and the MNA in the nucleus was counted in 50 cells/specimen. Results The MNAs in malignant cells in bile smear (9.6 ± 3.8) and tissue sections (9.2 ± 3.5) were significantly higher than those in the corresponding cells in benign biliary diseases (4.1 ± 1.0 and 2.9 ± 0.8, respectively; P < 0.01). The MNA of bile smear for both benign and malignant cells correlated significantly with that of tissue sections (r = 0.915; P < 0.0001). When the cutoff value of MNA for bile smear was set at 7.0, benign diseases could be discriminated from malignancy, and the MNA of 20 (80%) malignant specimens was higher than this value. Conclusions Our results suggest that the AgNOR dot count of cells in bile smears would be a useful diagnostic tool, in combination with conventional cytological diagnosis, before and during surgery.