[Proteins associated with nucleolar organizer regions: practical application in tumor histopathology and relationship to biological properties of the tumor].

The argyrophilic staining of nucleolar organizer regions (AgNOR) has been found to be of increasing use in routine and experimental histopathology in the study of certain neoplastic lesions. The AgNOR reaction demonstrates the presence of argyrophilic non-histone proteins within NORs. The number of detectable NORs depends on several factors: the level of transcriptional activity, the number of NOR-bearing chromosomes in the karyotype, and the stage of the cell cycle in which they are sought. In man, five chromosomes have NORs, and these areas are the sites which hybridize with rRNA and are of importance with respect to the ultimate synthesis of protein. The results of AgNORs might be more informative if this technique would be applied simultaneously in cytological and histological specimens for each patient. It may also be important to examine the AgNORs profiles in stromal cells.