tissue specimens taken from patients during operations or biopsies are usually assessed by the pathologists one or two days after the surgery . however , sometimes pathological results are needed urgently during the operation , while the patient is still on the operation table . in neurosurgical operations the need of a rapid diagnosis during the operation can be met by intraoperative consultation examinations . during surgeries , the use of touch preparation technique , known as touch preparation as an intraoperative consultation examination technique is now well established . a good intraoperative consultation examination technique should preserve good amount of tissue for paraffin embedded sections , and should be accurate and rapid . frozen section is another intraoperative consultation examination technique that needs more tissue and has some freezing artifacts . the architecture of tissues in frozen section closely approximates permanent histology sections , and enables a degree of comfort . touch preparation has been found quite reliable and useful in the determination of surgical resection margins , sentinel lymph nodes , adenomatous goiter , and confirmation of parathyroid tissue . various diagnoses can be well made by an expert pathologist using touch preparation technique , because the cytomorphological features of smears in every malignant or benign lesion are specific . the objective of the present study was to evaluate four years ( 2007 - 2011 ) of using touch preparation technique by shahid beheshti hospital pathologists to examine benefits and possible defects of the technique in determining the diagnosis of central nervous system biopsies taken during operations . the accuracy of the technique was judged against the diagnosis made by final pathological diagnosis . this study aimed at assessing the value of diagnosis made by touch preparation technique in 2007 - 2011 . all of the patients signed the written informed consent to include their data in the study . biopsies taken from lesions were grossly examined , and hemorrhagic and necrotic areas were sampled and prepared for the touch preparation technique . at least two smears were taken from each case by using two clean grease - free glass slides . the smears were fixed with absolute alcohol and were stained with geimsa and papanicolau . after the surgeries , remaining tissues were processed for paraffin - embedded sections , haematoxylin and eosin staining , and microscopic examination . the microscopic examination of paraffin sections , and touch preparation were made blindly by two pathologists . to examine the accuracy of diagnosis by touch preparation technique , the diagnoses obtained by this technique were compared with those obtained by microscopic examination of the smears . the findings were analyzed using statistical package for social sciences ( spss version 16 ) . during the study , 139 lesions , which had been sent for intraoperative consultation , were evaluated . the average patients age was 57 , and there were 70 males and 69 females . errors in diagnosis were seen in 12% of lesions . the highest correlation ( 100% ) was observed in five types of tumor , and no correct diagnosis was made in case of hydatid cyst . oligodendrogliomas , haemangioblastoma , meningioma , choroid plexus papilloma , craniopharyngioma , megakaryocytic leukemia , and dermoid cyst were diagnosed totally ( 100% ) correct ( table 1 ) .   the total number of tumor and correct diagnosis in touch preparation technique the accuracy of touch preparation technique for astrocytoma , pituitary adenoma , glioblastoma multiforme , metastatic carcinoma , and giant cell tumor was 81% , 84% , 66% , 66% , 88% and 80% , respectively . glioblastoma multiforme was misdiagnosed twice as metastasic carcinomas , and high grade astrocytoma was misdiagnosed five times as metastasic carcinomas . two cases of astrocytoma grade i was misdiagnosed as metastasic carcinomas , and one case of meduloblastoma was misdiagnosed as meningioma . other misdiagnosed tumors were reported as benign or malignant microscopic results or inflammation ( figure 1 - 6 ) . low grade astrocytoma : mild nuclear pleomorphism , mild to moderate hyperchromasia , absence of mitotic activity and dyscohesive pattern , minimal derivatium in nuclear shapes . left : permanent pathologic slide ( hematoxylline eosin x10 ) . glioblastoma multiform . left : permanent pathologic slide ( hematoxyllin eosinx10 ) , anaplastic and pleomorphic cells without glial processes and endothelial hyperplasia . meningioma : meningothelial cell proliferation with whorl formation . left : permanent pathologic slide ( hematoxyllin eosin x40 ) , indicators show whorl formation . right : touch preparation ( papanicolau 400 ) , the indicator shows the whorl formation . pitutary adenoma : diffuse sheet of uniform cells , fibrovascular stroma , and absence of pleomorphic cells . left : permanent pathologic slide ( hematoxyllin eosin x40 ) . hydatid cyst : cyst wall shows laminated layers and many scolexes . left : permanent pathologic slide ( hematoxyllin eosin x4 ) , the structures are visible . right : touch preparation ( papanicolau 100 ) , the structures are not visible thus the diagnosis is hard to be made . schwannoma . left : permanent pathologic slide ( hematoxyllin eosin 10 ) ; fusiform cells with long nuclei and eosinophilic cytoplasm arranged in hypercellular and hypocellular matrix . right : touch preparation ( papanicolau x40 ) ; a cluster of schwann cells with elongated nuclei . the present study was a retrospective analysis to determine the accuracy of touch preparation technique in diagnosing the type of tumors encountered during the operation . different authors used various stains such as 1% alcoholic toluidine blue and may - grunwald  giemsa . compared to frozen section , in touch preparation technique and a large area of tissue can be examined . besides , touch preparation technique provides enough tissue for intraoperative and subsequent routine paraffin section diagnoses . the two techniques are complementary , but frozen section is a better technique for the tissues , which their consistency is confirmed . unlike permanent histology , the frozen section technique , which has the accuracy rate of about 97% , can be done during the surgery . however , cryostat facility is not available at many centers in iran . touch preparation technique provides more crisp cytologic detail than frozen sections do , and can avoid most of freezing artifacts in brain tumors , high lipid content and soft nature . . the use of frozen section during surgery can give the surgeon the opportunity to avoid the second surgery . due to high predictive value , the touch technique can be used first in the operation room , and frozen section can be saved for cases with inconclusive diagnosis by the touch technique . this study is one of the largest studies of this technique on cns tumors in iran . previous reports indicate that the diagnostic accuracy of cytological smears ranged from 75% to 94% . in the present study the accuracy of touch preparation technique in diagnosing brain lesions was 84% , which is lower than that of other studies that included tumors only . this may be to the inclusion of other types of tumor such as bone tumors in the studies of neurosurgical tumors . the low diagnostic accuracy of touch preparation technique in our study may be related to limited sample size . the diagnostic accuracy of touch preparation technique for high and low grade astrosytoma was 81% ( 39 out of 48 ) in our study . when a small biopsy was submitted and typical features of pilocytic astrocytoma were not present , it was difficult to correctly diagnosis , or to grade the tumor . moreover , when vascular proliferation and atypia was interpreted without adequate clinical history , a misdiagnosis of high grade astrocytoma was made . when cellular pleomorphism , giant cells , mitoses necrosis and vascular proliferation were present , the diagnosis of glioblastoma was obvious ( figure 1 ) . because of high cellularity , pleomorphism and the round to polygonal appearance of the cells , high grade astrocytomas and glioblastoma are often confused with metastatic carcinoma . anaplastic and pleomorphic cells that have no glial process are the key point in the diagnosis glioblastoma multiforme . meningothelial , transitional and psammomatous meningiomas ( three types of meningiomas ) usually present no diagnostic difficulty because they exhibit features of non - neoplastic arachnoid cap cells , particularly the tendency to form whorls . the nuclei of many meningiomas ( especially the meningothelial types ) show two types of intranuclear vacuoles . one type is formed by invagination of cytoplasm into the nucleus and the other by clearing of chromatin material from the center of the nucleus . in addition to whorls , the presence of intranuclear inclusions and calcification is of help in diagnosing meningiomas . chordoid meningiomas were misinterpreted as chordoma and atypical meningioma with metastatic carcinoma . in haemangioblastomas , obtaining good quality smears was difficult . however , all of the cases of meningiomas and 10 out of 11 cases of schwannoma were diagnosed correctly , because of the mentioned diagnostic characteristics ( figure 3 and 6 ) . the cellular monomorphism and the absence of a significant reticulin network distinguish pituitary adenomas from non - neoplastic anterior pituitary parenchyma ( figure 4 ) . eleven of 13 cases were diagnosed correctly , but two cases were not diagnosed correctly using touch preparation technique .   in haemangioblastomas , obtaining good quality smears was difficult . the smears showed thick and dense trabeculae of elongated cells , which led to misinterpretation . all such characteristics helped correct diagnosing of all three cases of haemangioblastomas in our study . hydatid cysts are diagnosed by the presence of scolex and a cyst with a laminated layer ( figure 5 ) . touch preparation technique could not the two cases of hydatid cyst in our study . touch preparation technique is a rapid diagnostic method and a good complimentary technique for frozen section . the experience of a pathologist is very important as diagnosis is made on cytology alone without any special stains and in a short time . awareness of the cytomorphological features on smears of various lesions is important . in 64% of cases correct diagnosis could be made on smears alone , and in another 20% after clinical and radiological correlation . touch preparation technique is a very accurate and rapid method of intraoperative diagnosis , especially when combined with frozen section . however , adequate clinical history , neuroimaging details , and the intraoperative impression of the neurosurgeon , if provided , helps the neuropathologists to improve the diagnostic accuracy .
background : the touch preparation technique is an accurate and rapid method , and when used as intraoperative consultation examination technique it preserves a good amount of tissue for paraffin embedded sections . 
 this study aimed at examining the accuracy of the touch preparation technique by comparing its diagnosis with that of final pathological diagnosis made by microscopic examinations . 
 methods : the diagnoses of 139 central nervous system lesions by touch preparation technique and paraffin - embedded sections were compared . 
 results : touch preparation technique diagnosed correctly 118 ( 84% ) of the lesions . however , the technique failed to correctly diagnose 12% of the cases . 
 the highest rate of accurate diagnosis ( 100% ) was observed in five types out of 11 types of tumor examined . 
 however , the technique was not able to diagnose hydatid cysts correctly . 
 conclusion : the findings indicate that touch preparation technique may be useful in diagnosing tumor type during surgical operations . touch preparation technique is very accurate for intraoperative diagnosis . 
 however , adequate clinical history , neuroimaging details , and the intraoperative impressions of the neurosurgeons , if provided , help the pathologists to improve the diagnostic accuracy of the technique .