Squash Smear Technique in Rapid Intraoperative Diagnosis of Non-neoplastic and Cystic Lesions of CNS

Abstract

In neurosurgical practice, a rapid intraoperative diagnosis helps the neurosurgeon to monitor and modify the approach at surgery. Smears and frozen sections are the two rapid tissue preparations that may be used by neuropathologists for giving opinion on intraoperative biopsy specimens of suspected lesions. The smear technique, which could be either squash/crush smears or impression smears, has been applied in neurosurgical units worldwide. This method plays a very important role in the analysis of sample from craniotomies and the small specimens obtained from stereotactic biopsies. Squash smear technique is a very rapid technique and the study was designed to assess the accuracy of squash smear in the rapid intraoperative diagnosis of non-neoplastic and cystic lesions of CNS and to document the cytomorphology of these lesions. A total of 23 cases were studied. The tissue was removed at craniotomy or by burr hole biopsy. In all the cases clinicoradiological correlation was done with smear diagnosis. Smears were stained with 1% Toluidine blue and H&E. In all cases, results were compared with the paraffin section prepared from the tissue remaining after the squash smears. Immunohistochemistry was done in one case. Special stains were used as required. Amongst non-neoplastic lesions, tuberculous lesions comprised the maximum number of cases (n=9), two cases of PML, one case of fungal lesion, one case of non-specific abscess, one case of infarct, only reactive changes in one and normal cortex and white matter in one. In cystic lesions of the CNS, there was one case of Rathke’s Cleft cyst, four cases of Epidermoid cyst and two cases of arachnoid cyst. Cases of PML and Rathke’s cleft cyst could not be identified on smears. In all the cases, smear diagnosis was compared with histopathological diagnosis.