• Graeme Woodworth, Matthew J McGirt, Amer Samdani, Ira Garonzik, Alessandro Olivi, and Jon D Weingart.
• Departments of Neurosurgery and Oncology, Johns Hopkins School of Medicine, Baltimore, Maryland 21287, USA.
• Neurol. Res. 2005 Jun 1; 27 (4): 358-62.

ObjectivesTissue heterogeneity and rapid tumor progression may decrease the accuracy a prognostic value of stereotactic brain biopsy in the diagnosis of gliomas. Correct tumor grading is therefore dependent on the accuracy of biopsy needle placement. There has been a dramatic increase in the utilization of frameless image-guided stereotactic brain biopsy; however, its accuracy in the diagnosis of glioma remains unstudied.MethodsThe diagnoses of 21 astrocytic brain tumors were derived using image-guided stereotactic biopsy (12 frame-based, nine frameless) and followed by open resection of the lesion 1.5 (0.5-4) months later. The histologic diagnoses yielded by the biopsy were compared with subsequent histologic diagnosis from open tumor resection.ResultsHistology of 21 stereotactic biopsies accurately represented the greater lesion at open resection a median of 45 days later in 16 (76%) cases and correctly guided therapy in 19 (91%) cases. Biopsy accuracy of frameless versus frame-based stereotaxis was similar (89 versus 66%, p=0.21). In three (14%) cases, biopsy specimens were adequate to diagnose glioma; however, histology was insufficient for definitive tumor grading. Anaplastic oligodendroglioma (ODG) was under-graded as low-grade ODG in one (5%) case. Biopsy of new onset glioblastoma multiforme (GBM) yielded necrosis/gliosis and was termed non-diagnostic in one patient. Tumors <50 cm(3) were 8-fold less likely to accurately represent the grade of the entire lesion at resection compared with lesions <50 cm(3) (OR, 8.8; 95% CI, 0.9-100, p=0.05).DiscussionBoth frameless and frame-based MRI-guided stereotactic brain biopsy are safe and accurately represent the larger glioma mass sufficiently to guide subsequent therapy. Large tumor volume had a higher incidence of non-concordance. Increasing the number of specimens taken through the long dimension of large tumors may improve diagnostic accuracy.

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