Nucleolar organizer regions, stainable with the one-step silver colloid method (AgNORs), were evaluated for estimation of proliferative activity of pancreatic lesions, including ductal hyperplasias, dysplasias, adenomas, and adenocarcinomas induced by N-ethyl-N'-nitro-N-nitrosoguanidine (ENNG) in dogs and compared with values for proliferating cell nuclear antigen (PCNA) positive cells. The mean numbers of AgNORs per nucleus of cells in adenocarcinoma, dysplasia and hyperplasia cases were 2.37 (p<0.01), 2.03, and 1.48, respectively, the first two being clearly increased as compared to normal pancreatic duct cells (1.46). The PCNA labeling indices of adenocarcinoma, dysplasia and hyperplasia, at 38.9% (P<0.01), 13.1% (p<0.01), and 2.4%, respectively, were similarly and even more pronouncedly elevated over the normal pancreatic duct cell value (1.3%).
The present results suggest that numbers of AgNORs, like PCNA positivity, well reflect cell kinetics of lesions involved in dog pancreatic ductal tumorigenesis.