Diagnostic Correlation of Intraoperative Frozen Section and Squash Cytology with Histopathology in Central Nervous System Lesions: A 5-Year Retrospective Study from a Tertiary Care Center in South India

Intraoperative frozen section and squash cytology provide rapid diagnostic information that guides surgical management of central nervous system (CNS) lesions. Despite advances in neuroimaging and molecular diagnostics, these techniques remain valuable, although diagnostic challenges may occur due to limited sampling, tumor heterogeneity, and technical artifacts. This study evaluated their diagnostic accuracy and analyzed causes of discordance with final histopathology. To assess the diagnostic correlation of intraoperative frozen section and squash cytology with final histopathology in CNS lesions and identify causes of diagnostic discordance in a tertiary care center in South India. This retrospective descriptive study included 286 CNS lesions subjected to intraoperative frozen section and squash cytology between January 2021 and December 2025. Intraoperative diagnoses were correlated with final histopathology and categorized as concordant, discordant (misclassification, grading mismatch, or tumor vs. non-tumor), or inconclusive. Clinicoradiological and procedural factors associated with concordance were analyzed. Diagnostic performance was high, with a sensitivity of 94.6%, a specificity of 100%, a positive predictive value of 100%, and a negative predictive value of 95.5%. Overall concordance was 90%, with 6% discordant and 4% inconclusive cases. Concordance was significantly associated with radiological contrast enhancement, tumor type, and type of surgical procedure (p < 0.05). Sampling error, tumor heterogeneity, and technical artifacts were the major causes of discordance. Intraoperative frozen section and squash cytology demonstrate high diagnostic accuracy and remain valuable in the surgical management of CNS lesions. Recognition of factors contributing to discordance can improve intraoperative diagnostic accuracy and surgical decision-making.