Material and Method: The authors reviewed the histopathological results of 383 brain tumors, including IOFS and permanent histological diagnosis. The cases were classified into three diagnostic compatibilities (i) Perfect fit; the diagnosis of IOFS was identical to the permanent diagnosis, (ii) Partial compatibility; IOFS diagnosis was not incorrect but was too broad to be considered full compatibility, (iii) Conflict; IOFS diagnosis is completely different from the permanent diagnosis. The permanent diagnosis was used as a primary criterion and was compared to IOFS diagnosis and recurrence rate using different statistical methods.

Results: 84% of the patients underwent craniotomy and tumor resection, while 15% only underwent tumor biopsy. Approximately, 53.8 % of the cases revealed perfect matching in the diagnosis between IOFSs and permanent sections, while 16.2% of the cases revealed complete mismatching in the diagnosis between the sections. The remaining 30% of the cases showed partial compatibility in the diagnosis between the two diagnostic methods. There was no significant difference in recurrence rate among all cases of different diagnostic compatibility (p=0.54).