Reliability of histological diagnosis including grading in gliomas biopsied by image-guided stereotactic technique.

We report clinical and pathological data of 419 image-guided stereotactic biopsies. In the present series the diagnostic yield, estimated by comparing the original histological diagnoses with follow-up data, was found to be approximately 94% in gliomas. As it has been suggested that malignancy of astrocytic gliomas may be considerably underestimated in the small tissue samples obtained by stereotactic biopsy, we have reviewed 160 adult, diffuse supratentorial astrocytic tumours, correlating the original Kernohan tumour grades with survival. In this grading system, although there was generally a good correlation between histological grade and survival probability (P < 0.0001), no distinction could be made between the grade 3 (anaplastic astrocytoma) and grade 4 (glioblastoma) groups. Tumour grades obtained by applying the criteria of the more recent Daumas-Duport grading system were also determined and correlated with survival. These latter tumour grades not only correlated well with survival (P < 0.0001), but also enabled us to identify a group of patients with intermediate grade malignancy (grade 3, anaplastic astrocytoma), surviving longer than those with grade 4 tumours. Image-guided stereotactic biopsy is a useful means of providing tissue samples for histological diagnosis of brain neoplasms, including gliomas. Histological grading of adult, diffuse supratentorial astrocytic gliomas diagnosed by this technique is possible and should be carried out using an appropriate grading system.