Diagnostic value of silver nitrate staining for nucleolar organizer regions in cerebral astrocytic tumors

AIM: to compare the AgNOR's mean number with the histological type and grade of cerebral astrocytic tumors. MATERIALS AND METHOD: 16 primary cerebral astrocytic tumors (4 diffuse astrocytomas, 4 anaplastic astrocytomas and 8 glioblastomas) stereotactic biopsied in the Department of Neurosurgery, Clinical Hospital „Prof. Dr. N. Oblu” Iaşi, and histopathologically conventional diagnosed in Department of Neuropathology of the same hospital, were retrospectively identified. Tumor specimens were submitted to a combined staining technique: one – step silver nitrate method for AgNOR protein sites (modified after Ploton et al, 1986) counterstained with periodic acid-Schiff staining for basement membrane of vascular components. The mean AgNOR values (mAgNOR) for tumoral and vascular nuclei were determined. RESULTS: The average values of mean AgNORs/nucleus (mAgNOR/nucleus) presented a linear increase with increasing grade of malignancy from 1.96 for diffuse astrocytoma (GII), 2.34 for anaplastic astrocytoma (GIII), to 3.18 for glioblastoma multiforme (GIV). mAgNOR/tumoral nucleus also showed a linear correlation with the histological tumor grade: 2.27 for diffuse astrocytomas, 2.78 for anaplastic astrocytomas, and 3.35 for glioblastomas multiforme. A distinct difference between the mean values of AgNORs/vascular nucleus was expressed: 1.52 for diffuse astrocytoma (GII), 1.90 for anaplastic astrocytoma (GIII), and 3.18 for glioblastoma multiforme (GIV). There were some overlaps between GIII and GIV astrocytic tumors regarding the mAgNOR/tumoral nucleus: maximum value in anaplastic astrocytomas (GIII) was 2.91 and minimum value in small cells glioblastomas (GIV) was 2.47. Differentiation could be achieved with mAgNORs/vascular nucleus as no extreme value overlapped: maximum value in anaplastic astrocytomas (GIII) was 1.99 and minimum value in small cells glioblastomas (GIV) was 2.54. CONCLUSION: The malignancy grade of an astrocytic tumor can accurately be establish both on histological features of the conventional stained sample and on the average number, the shape and the distribution of AgNORs within tumoral and vascular nuclei, as AgNORs determinations supplement the histological information in small biopsies.