The diagnostic properties of frozen sections in suspected intracranial tumours – A study of 578 consecutive cases
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Background: Intraoperative frozen section (FS) diagnostics is an important diagnostic tool in neurosurgery, but agreement with final histopathological diagnoses may vary. The aim of this study was to assess the diagnostic properties of intraoperative frozen sections in suspected intracranial tumours. Methods: A retrospective review of consecutive patients operated with diagnostic biopsy or tumour resection for suspected intracranial brain tumours from January 2008 through December 2012 was performed. All 578 cases were both an intraoperative frozen section and a formalin-fixed paraffin-embedded (FFPE) section had been acquired, were included. Agreement with final diagnosis, sensitivity, specificity and predictive values were explored. Time between date of surgery and first final diagnosis based on FFPE section, whether the patients had undergone previous brain surgery and/or prior cerebral radiotherapy were also registered. Results: Agreement between FS diagnoses and final FFPE section diagnoses was seen in 504/558 (90.3%), while lack of agreement was seen in 54/558 (9.7%). In 20 cases agreement was not classifiable. Agreement was lower in low-grade gliomas (82.5%) than in high-grade gliomas (93.2%). Agreement between FS and FFPE was significantly higher in primary operations (92.1%) than in re-do operations (81.5%) (p=0.001). Sensitivity of FS ranged from 30.8% in lymphomas to 94.6% in meningiomas. Conclusions: Intraoperative frozen section diagnoses demonstrate high diagnostic accuracy. However, agreement varies among histopathological entities and is lower in low-grade tumours than in high-grade tumours. Sensitivity for diagnosing CNS lymphomas is low. A variable degree of reservation is always necessary when interpreting and communicating frozen section diagnoses.