Comparison of squash smears and frozen sections versus paraffin sections in the intra-operative diagnosis of central nervous system lesions

Abstract

Background: Utility of squash cytology is well established in the intra-operative diagnosis of brain tumors, thereby guiding the neurosurgeon in the surgical management. A comparative study between squash smears, frozen sections and paraffin sections was done with an aim to study the diagnostic accuracy as well as limitations of these techniques. The present study was also undertaken to evaluate the discordant cases in intraoperative consultation of central nervous system (CNS) lesions. Methods: A total of 221 neurosurgical specimens were received in the Department of Pathology over three years duration, of which intra-operative consultation was requested in 110 cases. Both frozen and squash preparation was performed on all cases and stained with hematoxylin and eosin. An intra-operative diagnosis was made after examination of the squash smears and frozen section slides. The diagnosis given on squash smears and frozen section were then compared with final diagnosis given on paraffin-embedded sections. Immunohistochemistry was performed in a few diagnostically challenging cases. Results: This study compares the diagnostic accuracy of squash smears and frozen sections from 110 surgical specimens. The 110 cases included thirty six astrocytomas (32.7%), twenty four meningiomas (21.8%), twelve schwannomas (10.9%), two hematolymphoid tumors (1.8%), eight medulloblastomas (7.3%), three oligodendrogliomas (2.7%), four pituitary adenomas (3.6%), four ependymomas (3.6%), four metastatic tumors (3.6%), one paraganglioma (0.9%), two pineal parenchymal tumors (1.8%) and ten infections (9.1%). The accuracy of squash smears was 93.6%, and when combined with frozen sections the accuracy increased to 97.3%. Conclusion: Squash smears are simple, rapid, economical and very effective tool in the diagnosis of brain tumors. However, in few matrix rich/fibrous tumors like meningiomas and schwannomas, frozen sections are more useful. Hence, overall the combined use of squash smear and frozen section study increases the intra-operative diagnostic accuracy of CNS lesions.