Intraoperative pathological diagnosis in 205 glioma patients in the pre-BCNU wafer era: retrospective analysis with intraoperative implantation of BCNU wafers in mind.

The present retrospective data analysis was performed to determine whether intraoperative pathological diagnosis (IOD) using frozen section (FS) could clearly distinguish high-grade glioma from WHO grade II gliomas. IOD was retrospectively compared to the pathological diagnosis using permanent paraffin sections (PS) of 205 glioma cases out of 356 brain tumor cases in the pre-Carmustine (BCNU) wafer era in Japan. The sensitivity and specificity of IOD regarding the whole glioma category were 96.1 and 98.0%, respectively. The positive predictive value and the underestimation ratio of glioma grading by IOD were 51.5 and 43.5% in all glioma cases. In addition, 54.5% of grade II glioma cases determined with IOD (grade II((FS))) were actually grade III or IV according to the PS pathology (grade III((PS)) or IV((PS)) cases). Recurrent cases and older age (≥50 years old) were predictive factors that resulted in underestimated grade II((FS)) group (grade II((FS))/III((PS)) + IV((PS))). The grade II((FS))/III((PS)) group tended to more frequently contain non-astrocytic tumors compared to the grade II((FS))/II((PS)) + IV((PS)) groups, although the difference was not statistically significant. In conclusion, the temporary WHO grade by IOD is underestimated in approximately half of glioma cases. We should pay attention to underestimation with IOD.