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central nervous system ( cns ) tumors are the tenth most common tumors in adults constituting 1.3% of all cancers and are the seventh leading cause of mortality in the developed countries .
intraoperative cytology preparation was first introduced by eisenhardt and cushing in the early 1930 and badt in 1937 .
this feature is exploited in squash smear as cytological details are easily seen in smears .
intraoperative squash smear technique is a very simple and rapid tool for diagnosis of brain tumors .
the present study was undertaken to assess the accuracy of intraoperative squash smear technique for cns tumors .
one hundred and fifty cases of cns space - occupying lesions were studied over a period of 15 months , from september 2013 to november 2014 .
the tissue obtained at the time of operation was crushed between the two clean glass slides with a pressure sufficient to spread the tissue into a film by the resident pathologist .
the smears were then fixed in 95% alcohol for 2 min and then stained with rapid hematoxylin and eosin staining method .
the smears were reported by the consultant pathologist taking into consideration the clinical and radiological findings , and the diagnosis was intimated to the neurosurgeon .
remaining tissue submitted for histopathology was later correlated with intraoperative cytology diagnosis by the same pathologist .
the study was a prospective study of 150 cns space - occupying lesions , which included 76 males and 74 females .
out of 150 cases studied , histopathological diagnosis was compatible with the cytological diagnosis in 141 cases . remaining seven cases showed discrepancy and two cases showed partial correlation as depicted in tables 2 and 3 .
the cases with the same diagnosis and grade on cytology and histopathology were considered as complete correlation .
the cases where intraoperative cytological diagnosis did not correlate with the histological examination were categorized as discrepant cases .
deviations of grade of tumor with lesser grade on squash smear cytology were included in partially correlated cases .
pie chart - incidence of central nervous system tumors in our series histological and cytological diagnosis of all the cases studied in our series discrepant cases ( histology vs. cytology ) partial correlation with an error in tumor grade in our series , astrocytomas ( incidence = 23.34% ) were the most common tumors , followed by schwannoma ( 14.67% ) , meningioma ( 13.33% ) , oligodendroglioma ( 8.67% ) , and pituitary adenoma ( 8% ) .
metastatic lesions were diagnosed in eight patients on squash smear which included metastasis from the breast , lung , and kidney .
( a ) high - grade astrocytoma : sheets of cells having large irregular pleomorphic nuclei ; mitotic figure ares seen ; ( h and e , 400 ) .
( b ) glioblastoma : thick - walled blood vessels ; ( h and e , 400 ) .
increase in cellularity with mild nuclear pleomorphism ; ( h and e , 400 ) .
( d ) pilocytic astrocytoma with loose and cellular area ; ( h and e , 100 ) .
( e ) pilocytic astrocytoma demonstrating eosinophilic granular bodies ; ( h and e , 400 ) .
more loosely adherent cells are smeared away from vessels ; ( h and e , 400 ) ( a ) oligodendroglioma showing finely branching capillary network ; ( h and e , 400 ) .
( b ) cellular smears of lymphoma showing isolated large round cells with scanty cytoplasm .
( c ) epidermoid cyst showing flakes of keratinous material ; ( h and e , 400 ) .
( d ) smears showing inflammatory cell infiltrate and macrophages ; ( h and e , 400 ) ( a ) medulloblastoma showing neoplastic cells in sheets and rosettes are present ; ( h and e , 400 ) . ( b ) meningioma showing whorled pattern of meningothelial cells ; ( h and e , 400 ) .
( c ) schwannoma showing interlacing fascicles of smeared antoni a tissue consisting of tightly packed , elongated spindle - shaped tumor cells ; ( h and e , 100 ) .
( d ) pituitary adenoma showing sheets of round cells having moderate amount of cytoplasm and at places arranged in the glandular pattern ; ( h and e , 400 )
the intraoperative diagnosis of cns tumors by smearing the tissue can provide guidance in modifying the surgical approach by the neurosurgeons .
the exact location , radiological findings , and clinical presentation of the patient help the pathologist in making the cytological diagnosis with reasonable accuracy .
accuracy of cytological diagnosis depends on the good cytological preparation and staining of the smear .
the soft and friable tissues in the cns tumors are easy to smear and thus provide good cellular details .
this is especially exhibited in gliomas , medulloblastomas , pituitary adenomas , most of the meningiomas , and metastatic tumors .
many tumors such as nerve sheath tumors , epidermoid cysts , and some meningiomas , especially the fibroblastic type , are relatively tough to smear .
although smears provide good cytological details , a few diagnostic difficulties were encountered due to misrepresentation of the tumor tissue .
two astrocytomas were misinterpreted as oligodendroglioma due to the presence of cortical tissue in the smears .
the absence of any rosette pattern with diffuse fibrillary background led to misinterpretation of two cases of ependymoma as astrocytoma . in these cases of ependymoma , discussion with the operating surgeon could have helped in knowing the plane of cleavage of the tumor and thereby keeping ependymoma as a differential diagnosis , thereby eliminating the error .
representative tissue was not submitted and gliotic tissue was misinterpreted as pilocytic astrocytoma . in cases when the tissue is not representative or the cytology findings are not consistent with the radiology , at times , we can ask for more tissue to be submitted intraoperatively which would reduce the discrepancy .
desmoplastic infantile ganglioglioma was reported as low - grade glioma due to absence of ganglion cells in the tissue submitted . in the present study ,
there were two partially correlated cases which varied in the grade on cytology and histopathology .
the grade of astrocytomas varies within a single tumor , and hence , grading of astrocytoma on cytology occasionally poses problem .
one case of glioblastoma was under graded as anaplastic astrocytoma due to the absence of necrosis and no thick - walled vessels could be appreciated .
another case of anaplastic astrocytoma was misgraded as low - grade astrocytoma due to only occasional mitoses in the smear sampled . in our study , the overall diagnostic accuracy was found to be 94.0% .
it permits reliable intraoperative guidance . with clinicoradiological correlation , squash smear cytology could be the preferred method for intraoperative diagnosis of cns tumors .
background : intraoperative squash smear cytology is a simple and reliable technique for rapid intraoperative diagnosis of neurosurgical specimens . the study was designed to assess the accuracy of intraoperative squash smear in the diagnosis of central nervous system ( cns ) space - occupying lesions.materials and methods : one hundred and fifty cases of cns space - occupying lesion were studied in a period of 15 months . 
 smears were prepared from the biopsy sample obtained at the time of operation and were stained with rapid hematoxylin and eosin method.results:one hundred and forty - one cases showed complete correlation with histopathology , two cases showed partial correlation , and seven cases were discrepant . 
 the overall diagnostic accuracy was found to be 94%.conclusion : intraoperative squash smear thus provides diagnosis with fair accuracy in brain tumors and is of great value in intraoperative consultation .