AgNOR area in interphase nuclei of human tumours correlates with the proliferative activity evaluated by bromodeoxyuridine labelling and Ki-67 immunostaining.

The area of silver-stained proteins associated with interphase nucleolar organizer regions (AgNORs) was compared with labelling data obtained by bromodeoxyuridine (BrdU) incorporation and Ki-67 immunostaining in 25 tumours of different origins and two non-neoplastic lesions of the thyroid. Our data demonstrate a highly significant correlation between the mean area occupied by the AgNOR proteins measured by an image processing system and the proliferative indices evaluated by BrdU labelling (r = 0.89, P less than 0.001) and Ki-67 immunostaining (r = 0.86, P less than 0.001). AgNOR protein area measurement is therefore proposed as a simple, inexpensive, and reliable method of evaluating the proliferative activity in routinely processed tumour samples.