Background: Intraoperative cytology preparation was first introduced by Eisenhart and Cushing in early 1930s. With the advent of CT and MRI guided stereotactic biopsies, smear technique has gained importance because of technical simplicity and good preservation of cytological and nuclear details at low expense. Aims: 1. To study various patterns of central nervous system [CNS] lesions in squash cytology and histopathology. 2. To correlate cytological diagnosis with histopathology. 3. To evaluate the diagnostic utility of intraoperative squash cytology. Settings and Study Design: Analytical study at tertiary care hospital. Material and Methods: Hundred cases were analyzed. Squash smears were prepared from biopsy samples sent in isotonic saline. The smears were stained by Hematoxylin and Eosin [H &E] and Papaniculaou [PAP] stain. Histopathological evaluation was done subsequently from biopsy samples sent in formalin. Special stains were performed in selected cases. Cytomorphological features were correlated with histopathology. Statistical Analysis: Frequencies, ChiSquare Test and Crosstabs were used for calculation. Results: Histopathological diagnosis of hundred cases included neoplastic lesions [90%] and nonneoplastic lesions [10%]. Correct diagnosis was achieved by squash cytology in 68 cases [73.11%] by complete correlation. However, diagnostic accuracy improved considerably [84.94%] after applying partial correlation criteria. For the detection of neoplastic lesions, squash cytology had sensitivity of 95.29%, specificity of 75% and efficacy of 93.54%. The p value, determining efficacy of squash cytology for detecting CNS neoplasms was statistically significant [p<0.005]. Conclusions: Squash cytology is a reliable, rapid and inexpensive intraoperative diagnostic tool. It has high sensitivity and is highly efficacious procedure.

Keywords: Neurosurgical; Squash Cytology; Histopathology; IntraOperative; Diagnostic Accuracy.