Histological grading and bromodeoxyuridine labeling index of astrocytomas. Comparative study in a series of 60 cases.

The histological grade and the bromodeoxyuridine (BUdR) labeling index of 60 astrocytomas of "ordinary" cell types (fibrillary, protoplasmic, gemistocytic, and anaplastic astrocytomas and glioblastomas) were compared to determine whether the grading system reflects the proliferative potential of the tumors. The tumor grade was based on the presence or absence of four criteria (nuclear abnormalities, mitosis, necrosis, and vascular endothelial proliferation): Grade 1, no criterion, Grade 2, one criterion, Grade 3, two criteria; and Grade 4, three or four criteria. The BUdR labeling index, or percentage of S-phase cells, was calculated in paraffin-embedded tumor sections after in situ labeling by intraoperative intravenous infusion of BUdR, 200 mg/sq m. Exponential regression analyses showed a positive correlation between the histological grade and labeling index (r = 0.88, p less than 0.001) that was stronger than the correlations between log labeling index and age (r = 0.55, p less than 0.001) and between grade and age (r = 0.55, p less than 0.001). These results indicate that the histological grading system reflects the proliferative potential of "ordinary" astrocytomas.