Analysis of Intraoperative Squash Cytology of Central Nervous System Lesions and its Correlation with Immunohistopathology and Radiology.

Context: Central nervous system lesions are diverse and remain one of the most challenging domains for neuropathologists. Intraoperative cytological diagnosis is now a universally accepted technique in diagnosis of central nervous system (CNS) lesions.

Aims: 1) To analyze and compare cytomorphological features of CNS lesions in intraoperative squash smears with histopathology, immunohistochemistry, and preoperative radiological diagnosis and 2) to determine the diagnostic accuracy, sensitivity, and specificity of intraoperative squash cytology.

Settings and design: Prospective study conducted at a tertiary healthcare centre over a period of two years.

Methods and material: All biopsy materials which underwent squash cytology and histopathological examination were collected, evaluated, classified, and graded according to WHO classification of CNS Tumors, 2016. The squash cytosmear diagnosis was compared with histopathological features and radiological diagnosis. Discordances were evaluated.

Statistical analysis used: The cases were categorized into true positives, false positives, true negatives, and false negatives. Diagnostic accuracy, sensitivity, and specificity were calculated from 2*2 table.

Results: A total of 190 cases were included in the study. A total of 182 cases (95.70%) were neoplastic of which 87.36% were primary CNS neoplasms. Diagnostic accuracy in non-neoplastic lesions was 88.8%. Most common neoplastic lesions were glial tumors (35.7%), meningioma (17.3%), tumors of cranial and spinal nerves (12%), and metastatic lesions (12%). Diagnostic accuracy of squash cytology was higher in glial tumors (93.8%), meningioma (96.7%), and metastatic lesions (95.45%). Diagnostic accuracy of radiological modalities was 85.78%.

Conclusions: A good familiarity with cytomorphological features of CNS lesions, clinical details, radiological findings, and intraoperative impression of neurosurgeon enables the pathologist to improve diagnostic accuracy and reduce errors.