MRI-guided stereotactic biopsy in the diagnosis of glioma: comparison of biopsy and surgical resection specimen.

BACKGROUND: Although there has been a dramatic increase in the accessibility and utilization of high-resolution MRI techniques for the evaluation of brain tumors, there is currently only a single report comparing stereotactic brain biopsy specimen to subsequent resection specimen exclusively in the management of gliomas.
METHODS: The diagnoses in 43 cases of astrocytic brain tumors were derived using MRI-guided stereotactic biopsy followed by open resection of the lesion. The histologic diagnoses yielded by biopsy were compared with subsequent histologic diagnosis after open tumor resection. All biopsies and histologic diagnoses were made by the same surgeon and pathologist, respectively.
RESULTS: In 23 patients undergoing resection <60 days after biopsy, the biopsy diagnosis was consistent with resection diagnosis in 18 cases (79%) and led to the correct treatment in 22 cases (96%). Recurrent glioblastoma multiforme (GBM) was undergraded as anaplastic astrocytoma in 4 patients. GBM was misdiagnosed as radiation necrosis in 1 patient. MR-nonenhancing lesions [10/10 (100%)] yielded histology that correlated with subsequent craniotomy, while only 8/13 (61%) MR-enhancing lesions yielded histology that was consistent with that at craniotomy (p < 0.05). In 20 patients undergoing resection because of radiologic tumor progression (mean 7 months after biopsy), 6/6 (100%) biopsy diagnoses of a specific glioma grade correlated with resection diagnosis, while only 6/14 (43%) biopsy diagnoses of radiation effect correlated with resection diagnosis (p < 0.01).
CONCLUSION: MRI-guided stereotactic brain biopsy specimen accurately represents the grade of the larger glioma mass sufficiently to guide subsequent therapy. Enhancement on MR may be a negative prognostic indicator of biopsy accuracy.