Smear technique in the intra-operative brain tumor diagnosis: its advantages and limitations.

The role of intra-operative pathological diagnosis increases along with a development of minimally invasive neurosurgery, especially stereotactic and endoscopic techniques. The authors present their own experience with the cytological method and evaluate its usefulness in intra-operative diagnosis of brain tumors. Brain tumor biopsy specimens obtained during craniotomy from 217 patients were examined. The cytological preparations (smears) were stained with 1% toluidin blue and/or with May-Grünwald-Giemsa stain. In 199 cases (92%) the cytological diagnosis was consistent with the histopathological one. A 99% sensitivity and 69% specificity were obtained. The histogenesis of gliomas was correctly established in 90% and their grade in 73% of cases. The most frequent diagnostic errors were: undergrading of gliomas (20), incorrect assessment of their histogenesis (10), diagnosis of low grade astrocytoma in a case of gliosis (3) and diagnosis of glioblastoma multiforme instead of metastatic carcinoma (2 cases). The most important advantages of cytological examination are rapidity, simplicity and relatively high diagnostic efficacy. Even very tiny specimens, especially of soft consistency are suitable for this technique, which is extremely important in operations of brain tumors localized in functionally important brain areas. In the authors' opinion this method still merits wider popularization in neurosurgical centers.