Nucleolar organizer regions (AgNORs) in primary and recurrent gliomas. A retrospective study

To assess the diagnostic and prognostic relevance of nucleolar organizer regions (AgNORs) the silver-stained AgNOR structures of 46 human gliomas (22 primary gliomas, 21 first and 3 second recurrences) from 28 patients were counted and measured. Surgical specimens of two neuropathological centres were included in this retrospective study. The tumours were classified into 8 groups according to WHO criteria of diagnosis and grading and their state of recurrence: 1: primary glioma grade II; 2: primary glioma grade III; 3: glioblastoma grade IV; 4: first recurrence of glioma grade II; 5: first recurrence of glioma grade III; 6: first recurrence of glioblastoma grade IV; 7: second recurrence of glioma grade II and 8: second recurrence of glioma grade III. AgNOR numbers demonstrated a positive correlation with increasing histological grade. Similarly, higher levels of AgNORs were in general found in recurrent tumours compared to primary tumours with few exceptions in groups, in which few numbers only could be analyzed. The present study demonstrates the utility of evaluating AgNOR in assessing malignant gliomas and indicates that recurrences have a higher proliferative potential than original tumours. The problems of standardization of the AgNOR technique are especially crucial for the retrospective evaluation of fixed and embedded pathological material.