Intraoperative squash cytology: accuracy and impact on immediate surgical management of central nervous system tumours

Abstract

To assess the diagnostic accuracy of squash cytology, reasons for deferment, disagreement and partial agreement, and assess its impact on immediate surgical management of central nervous system tumours. All cases of squash cytology received from January 2007 to July 2010 were reviewed and correlated with final histopathological diagnoses. Deferments, disagreements and partial disagreements were reviewed to look for possible reasons. The impact of disagreements and partial agreements on immediate surgical management was evaluated in consultation with neurosurgeons. Overall accuracy (including complete and partial agreement) for squash smear diagnosis of 334 cases was 94.9% while complete agreement was 79.9%, excluding deferred cases. Disagreement was seen in 17 cases and 31 cases were deferred for final histopathology diagnosis. Good correlation was seen in astrocytoma, meningioma, schwannoma, medulloblastoma, pituitary adenoma and metastatic carcinoma, whereas poor correlation was seen in oligodendroglioma, ependymoma and lymphoma. Among 17 cases with disagreement and 50 cases with partial agreement, an adverse impact on immediate surgical management was found in six (35.3%) cases and one (2.0%) case, respectively. The sensitivity and specificity of squash for diagnosis of neoplastic lesions were 98.7% and 87.5%, respectively. Squash cytology is a rapid, reliable, simple technique for intraoperative consultation in neurosurgical practice with high overall accuracy. Causes causing an adverse impact on surgical management were rare and potential avoidable reasons for them were identified.