Nucleolar organizer regions (AgNORs) in astrocytic tumors

79 astrocytic tumors classified according to the WHO classification and stained with a modified AgNOR staining technique were analysed with the help of an automatic image analysing system. The number and area of AgNORs were determined. The mean AgNOR number per nucleus was 1.28 in pilocytic, 1.98 in differentiated, 2.84 in anaplastic astrocytomas, 3.33 in small cell glioblastomas and 4.24 in multiforme glioblastomas. The area of all AgNORs per cell ranged from 0.95 microns2 (pilocytic astrocytomas), 1.53 microns2 (differentiated astrocytomas), 2.73 microns2 (anaplastic astrocytomas), 3.1 microns2 (small cell glioblastomas) to 4.12 microns2 (multiforme glioblastomas). With regard to AgNORs there are little differences between anaplastic astrocytomas and small cell glioblastomas.