Background: Representative sampling of gliomas at biopsy is essential for correct assignation of histologic grade and subsequent patient management. If sampling is unrepresentative, tissue devoid of mitoses or necrosis may be obtained and result in a falsely low glioma grade.
Objective: To assess whether the MIB-1 labeling index of glioma tissue cores specifically constructed so as to replicate ‘unrepresentative’ astrocytoma biopsies would predict the real or actual glioma grade.
Methodology: Tissue microarrays were prepared from 134 samples of low-grade astrocytoma [WHO Grade II] , anaplastic astrocytoma and glioblastoma multiforme. Donor blocks were sampled to avoid mitoses, necrosis and endothelial hyperplasia. Immunohistochemistry was performed using the Ki-67 (MIB-1) proliferation marker and the percentage of MIB-1 positive cells per core was calculated.
Results: Mean MIB-1 % values for LGA (n=47), AA (n=38) and GBM (n=46) were 0.54 (+/-0.82), 5.68 (+/-6.69) and 7.21 (+/-7.98); ranges 0-3.07; 0–30.08 and 0–29.08 respectively. A MIB-1 % count of >3.07 excludes LGA, but a MIB-1 % count of <3.07 does not exclude GBM or AA.
Conclusion: In unrepresentative glioma biopsy material, MIB-1 labeling may be used to exclude low-grade astrocytoma, but cannot be used to distinguish between GBM and AA.
- tumour grading