Location of nucleolar organizer regions (AgNORs) in the nuclei of astrocytic tumors.

Seventy-nine astrocytic tumors classified according to the WHO classification and stained with a modified AgNOR staining technique were analyzed with the help of an automatic image analyzing system. With increasing malignancy there is an increase of AgNORs per cell. Furthermore, AgNORs move from a more central to a more peripheral position within the nucleus, thus leading to a significant increase of the AgNOR count at the periphery of the nucleus. An inverse relation was found at the center. With regard to AgNORs, there are little differences between anaplastic astrocytomas and small cell glioblastomas. The most striking differences were seen between differentiated (grade 2) and anaplastic (grade 3) astrocytomas.