Diagnostic Utility of Squash Smear Cytology in Intraoperative Evaluation of CNS Tumors: A Cyto-Histopathological Correlation Study

Background: Central nervous system (CNS) tumors require rapid intraoperative diagnosis to guide surgical management. Squash smear cytology is a simple, rapid, and cost-effective technique widely used for this purpose. This study evaluates its diagnostic accuracy by correlating cytological findings with final histopathology and immunohistochemistry (IHC). Material and Methods: This cross-sectional analytical study included 50 patients underwent neurosurgical procedures for intracranial space-occupying lesions at IGMC Shimla. Fresh tissue was used to prepare squash smears stained with Leishman and rapid H&E, while remaining tissue underwent routine histopathology with selective IHC. Cytological findings were correlated with histopathology, the gold standard, and diagnostic indices were calculated using Epi Info 7.2.5.0. Results: Patients ranged from 12–86 years (mean 46.3 years) with slight male predominance (54%). Cytologically, meningioma (40%) and high-grade astrocytoma (38%) were most common. Histopathology confirmed meningioma in 40% and high-grade gliomas in 34% of cases, with a wide spectrum of additional tumors. Overall cyto-histological concordance was 90%, with 100% accuracy for high-grade gliomas, oligodendroglioma, SEGA, hemangioblastoma, metastatic carcinoma, eosinophilic granuloma, and choroid plexus carcinoma. Meningioma accuracy was 95%. Discordance (10%) resulted from hemorrhagic smears, poor spreading, spindle-cell mimics, or inadequate samples. Sensitivity was 92%, PPV 100%, and overall diagnostic accuracy 90%. Conclusion: Squash smear cytology is a rapid, accurate, and dependable intraoperative diagnostic tool for CNS tumors, demonstrating excellent concordance with histopathology and strong diagnostic performance across a wide tumor spectrum.

Keywords: Squash Smear Cytology, CNS Tumors, Intraoperative Diagnosis, Histopathology, Immunohistochemistry.