Validity of stereotactic biopsy as a diagnostic tool.

254 patients affected by intracranial lesions underwent stereotactic biopsy in our department from 1978 to 1986. Target localization was achieved by CT. Multiple biopsy sampling was performed by cup microforceps or sliding cannula. Operative mortality was limited to 2 cases. Definitive tumour diagnosis including type and approximate grading was obtained in 211 (83%) patients. Diagnostic failures have been investigated from the neuroradiological point of view. Failure rate is low in solid tumours with CT homogeneous appearance and clear-cut borders, gradually increases in non homogeneous tumours, necrotic haemorrhagic or cystic, and is high in non classifiable lesions, generally hypodense at CT, with indefinite borders. In the authors opinion the variability of diagnostic retrieval in different types of lesions must be taken into account when proposing stereotactic biopsy.