Does imprint cytology of brain tumours improve intraoperative diagnoses?

Unveiling the potential application of intraoperative brain smear for brain tumor diagnosis in low-middle-income countries: A comprehensive systematic review

Background

Immediate intraoperative histopathological examination of tumor tissue is indispensable for a neurosurgeon to track surgical resection. A brain smear is a simple, rapid, and cost-effective technique, particularly important in the diagnosis of brain tumors. The study aims to determine the effectiveness of intraoperative brain smear in the diagnosis of brain tumors in low- and middle-income countries (LMICs), while also evaluating its sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV), and overall accuracy.

Methods

A comprehensive search of the literature was conducted using PubMed, Scopus, and Google Scholar. The retrieved articles were independently screened by two reviewers. The data was extracted, processed, and organized using Microsoft Excel.

Results

A total of 59 out of 553 articles screened were included in the final analysis. The sensitivity and specificity of the intraoperative smear of brain tumors were found to be over 90% in most studies. The PPV was consistently above 90% in 11 studies, reaching 100% in one study and the NPV varied, ranging from 63% to 100%, and the accuracy was found to be >80% in most studies. One recurrent theme in the majority of the included studies was that an intraoperative brain smear is a cost-effective, quick, accessible, and accurate method of diagnosing brain tumors, requiring minimal training and infrastructure.

Conclusion

Intraoperative brain smear is a simple, rapid, cost-effective, and highly sensitive diagnostic modality for brain tumors. It can be a viable and accessible alternative to more traditional methods such as frozen sections and can be incorporated into neurosurgical practice in LMICs as a reliable and efficient diagnostic tool.

Intraoperative consultation in the diagnosis of posterior fossa brain tumors following the 2016 WHO update

OBJECTIVE

Intraoperative crush/squash smear or frozen section consultation is routinely performed at several centers and offers rapid onsite assessment of tumor type and provides invaluable information to the neurosurgeons. The WHO classification of central nervous system neoplasms underwent a paradigm shift in 2016 with the incorporation of molecular data with the morphological features, such that several new entities came to be distinctly defined. With this paper, we present our experience at intraoperative consultation of brain tumors arising in posterior fossa and aim to apprise the pathologists with the spectrum of cytomorphologic appearances that can occur during such consultation and highlight the diagnostic dilemmas and pitfalls encountered in this setting.

METHODS

This is a retrospective observational study illustrating the salient morphological features of commonly encountered brain tumors arising in the posterior fossa (prototype example of each type) reported at our institute over a period of seven years. Both squash smears and rapid snap frozen section were prepared and stained with Toluidine blue and rapid hematoxylin and eosin (H&E) stains.

RESULTS AND CONCLUSIONS

While the majority of tumors at this location comprise of pilocytic astrocytoma, ependymoma, and medulloblastoma, some rare examples may also arise; common differentials must be considered and prudently excluded to arrive at the diagnosis which is crucial in guiding the neurosurgeon. Both squash smears and rapid frozen section should be prepared and complement each other for rapid on-site evaluation.

Confocal Laser Endomicroscopy Assessment of Pituitary Tumor Microstructure: A Feasibility Study

This is the first study to assess confocal laser endomicroscopy (CLE) use within the transsphenoidal approach and show the feasibility of obtaining digital diagnostic biopsies of pituitary tumor tissue after intravenous fluorescein injection. We confirmed that the CLE probe reaches the tuberculum sellae through the transnasal transsphenoidal corridor in cadaveric heads. Next, we confirmed that CLE provides images with identifiable histological features of pituitary adenoma. Biopsies from nine patients who underwent pituitary adenoma surgery were imaged ex vivo at various times after fluorescein injection and were assessed by a blinded board-certified neuropathologist. With frozen sections used as the standard, pituitary adenoma was diagnosed as “definitively” for 13 and as “favoring” in 3 of 16 specimens. CLE digital biopsies were diagnostic for pituitary adenoma in 10 of 16 specimens. The reasons for nondiagnostic CLE images were biopsy acquisition <1 min or >10 min after fluorescein injection (n = 5) and blood artifacts (n = 1). In conclusion, fluorescein provided sufficient contrast for CLE at a dose of 2 mg/kg, optimally 1–10 min after injection. These results provide a basis for further in vivo studies using CLE in transsphenoidal surgery.

An update on touch preparations of small biopsies

Touch preparations (TPs) are being increasingly utilized in the era of personalized medicine. They fill a gap in cytopathology practice by providing a method to perform rapid onsite evaluation of small tissue samples such as core needle biopsies. However, there is a paucity of literature about how best to perform and interpret a TP. A high-quality TP can provide excellent diagnostic accuracy and good concordance with core needle biopsy histopathology findings. Although many of the cytomorphologic features of TPs overlap with fine needle aspirate smears, TP cytology is unique and differs from conventional smears in many aspects. It is important for cytologists to recognize these features, as well as potential pitfalls and artifacts in order to avoid misinterpretation. Core depletion of tumor cells is a notable drawback if TPs are performed too aggressively. TP slides are also valuable for ancillary testing because they often contain a cellular and pure population of whole tumor cells. This paper reviews all of the aspects of TPs including their clinical utility, proper slide preparation techniques, distinctive cytomorphologic characteristics, limitations, and potential pitfalls.

Diagnostic Accuracy of Cytology Smear and Frozen Section in Glioma

Glioma is the commonest primary intracranial tumour and it has been the most predominant tumour in many studies. It accounts for 24.7% of all primary brain tumour and 74.6% of malignant brain tumour. Intraoperative diagnosis plays a crucial role in determining the patient management. Frozen section has been the established technique in providing rapid and accurate intraoperative diagnosis. However due to some disadvantages like ice crystal artefact, high expenditure and requirement of skilled technician, there is increase usage of cytology smear either replacing or supplementing frozen section technique. The aim of this review is to determine the diagnostic accuracy of cytology smear and frozen section in glioma and to see whether there is significant difference between those techniques. The overall diagnostic accuracy for frozen section in glioma ranging from 78.4% to 95% while for cytology smear, the diagnostic accuracy ranging from 50% to 100%. Based on certain literatures, no statistically difference was observed in diagnostic accuracy of cytology smear and frozen section. Thus, cytology smear provides an alternative method in establishing intraoperative diagnosis. Both cytology smear and frozen section are complimentary to each other. It is recommended to use both techniques to improve the diagnostic accuracy in addition with adequate knowledge, clinical history, neuroimaging and intraoperative findings.

Vessel Morphologies of the Brain in Cytological Squash Preparations Are Useful for Intraoperative Diagnosis of High-Grade Astrocytomas

OBJECTIVE

The aim of this study was to determine whether intraoperative cytological evaluation of squash preparations is of benefit for differentiating high-grade from low-grade astrocytomas.

METHODS

Squash preparations of 42 astrocytomas were classified histologically according to the World Health Organization (WHO) 2007 classification system as grade II (n = 12), grade III (n = 11), and grade IV (n = 19) and were divided into 2 groups, namely a low-grade group (grade II) and a high-grade group (grades III and IV). The focus was on morphological cell and vessel characteristics, namely nuclear atypia, chromatin pattern, nuclear enlargement, variation in nuclear size, the presence of nucleoli, mitosis, tumor necrosis, cell density, multibranched vessels, and vascular dilatation, and these characteristics were compared between the low- and high-grade groups.

RESULTS

Nuclear atypia, the presence of coarse chromatin, variations in nuclear size, and cell density ≥200 per high-power field were significantly more prevalent in high- than in low-grade astrocytomas (p = 0.0407, p < 0.01, p < 0.01, and p < 0.01, respectively). Vessels with > 3 branches and a mean vessel diameter ≥20 μm were more prevalent in high- than in low-grade astrocytomas (p < 0.01).

CONCLUSION

Squash preparation cytology provides added benefit for the intraoperative identification of high-grade astrocytoma.

Evaluation of Intraoperative Cytological Smears for Diagnosis of Brain Tumors with Special Reference to Immunohistochemistry

Context:

Brain tumors are heterogeneous group of benign and malignant tumors of glial, meningeal, neuronal, embryonal, and lymphoid origin. Rapid intraoperative diagnosis of the nature of the tumor helps the surgeon to plan the extent of surgery and modify it accordingly.

Aims:

(1) To establish the validity and reliability of squash cytology in the intraoperative diagnosis of brain tumors. (2) To correlate with histopathological report and immunohistochemistry (IHC) profile.

Settings and Design:

Prospective, observational study.

Subjects and Methods:

prospective, observational study was conducted in the Department of Pathology in collaboration with the Department of Neurosurgery of a tertiary care hospital. One hundred and seven patients with symptomatic or radiologically detected brain tumors were included in the study. Intraoperative squash smears were stained with hematoxylin and eosin and rapid papanicolaou stain. Cytological diagnosis was recorded and communicated to the surgeon. Cytological findings were corroborated with histological findings subsequently. GFAP, Ki-67, and ER-PR IHC were used as additional markers.

Statistical Analysis Used:

Software used in statistical analysis of our study was MedCalc version 11.6 (Mariakerke, Belgium: MedCalc Software 2011).

Results:

A total of 107 cases were included in the study. Meningioma was the most common lesion. Overall sensitivity in our study to diagnose benign and malignant tumors was 94.7% and the specificity is 97.6% with positive and negative predictive value of 94.7% and 97.6%, respectively. Diagnostic accuracy was highest in pituitary adenoma.

Conclusions:

The combination of meticulous evaluation of clinical, radiological, and cytological findings helps in accurate and rapid diagnosis of brain tumors.

Correlation of Intraoperative Frozen Section Report and Histopathological Diagnosis of Central Nervous System Tumors - A Six-Year Retrospective Study

OBJECTIVES

To evaluate the degree of agreement between the intraoperative frozen section (FS) reporting of central nervous system (CNS) tumors and final histopathological diagnosis based on permanent paraffin section.

METHODS

All CNS tumor cases with a diagnosis at FS and subsequent permanent section (n = 261) taken from 2007 to 2012 were retrospectively reviewed. Twenty percent of FS were double-checked by a senior pathologist as part of the study and the intraobserver agreement between the pathologist and the agreement between final report, and initial FS report was estimated by the intraclass correlation coefficient (ICC).

RESULTS

A total of 261 cases were reviewed. The most common diagnosis was glioblastoma (grade IV) and meningioma (grade I-II) forming 45.6% of cases. Fifty-three cases were subjected to intraobserver agreement of histological diagnosis. There was nearly perfect intraobserver agreement on histopathology (ICC = 0.9). Out of 261 cases, 224 cases showed a strong agreement between the FS diagnosis and final histological diagnosis (ICC = 0.747). A discrepancy between the FS and final diagnosis were found in eight cases. The disagreement did not relate to any specific tumor type. However, in three cases, the discrepancy was in the grading of the glioma. In 29 cases, a definite opinion could not be given on FS as the samples examined were nonrepresentative.

CONCLUSIONS

Histopathological slides classified by World Health Organization criteria of CNS tumors had excellent intraobserver agreement. Our results show a moderate to high degree of agreement in the intraoperative diagnosis of CNS lesions using FS. However, there are limitations, and some lesions are a diagnostic challenge. There is a need to improve our diagnostic skills and knowledge of possible errors and establish better communication with neurosurgeons.

The isolated perfused human skin flap model: A missing link in skin penetration studies?

Development of effective (trans)dermal drug delivery systems requires reliable skin models to evaluate skin drug penetration. The isolated perfused human skin flap remains metabolically active tissue for up to 6h during in vitro perfusion. We introduce the isolated perfused human skin flap as a close-to-in vivo skin penetration model. To validate the model's ability to evaluate skin drug penetration the solutions of a hydrophilic (calcein) and a lipophilic (rhodamine) fluorescence marker were applied. The skin flaps were perfused with modified Krebs-Henseleit buffer (pH7.4). Infrared technology was used to monitor perfusion and to select a well-perfused skin area for administration of the markers. Flap perfusion and physiological parameters were maintained constant during the 6h experiments and the amount of markers in the perfusate was determined. Calcein was detected in the perfusate, whereas rhodamine was not detectable. Confocal images of skin cross-sections shoved that calcein was uniformly distributed through the skin, whereas rhodamine accumulated in the stratum corneum. For comparison, the penetration of both markers was evaluated on ex vivo human skin, pig skin and cellophane membrane. The proposed perfused flap model enabled us to distinguish between the penetrations of the two markers and could be a promising close-to-in vivo tool in skin penetration studies and optimization of formulations destined for skin administration.

Intraoperative diagnosis of central nervous system lesions: Comparison of squash smear, touch imprint, and frozen section

Background:

Intraoperative diagnosis of central nervous system (CNS) lesions is of utmost importance for neurosurgeons to modify the approach at the time of surgery and to decide on further plan of management. The intraoperative diagnosis is challenging for neuropathologists.

Aims:

The study was undertaken to determine the accuracy of cytological techniques (crush smears and touch imprints), frozen sections of space occupying lesions of the CNS and compare it with histopathological diagnosis.

Materials and Methods:

A total of 75 specimens received intraoperatively were subjected to cytology and frozen section study.

Results:

Neoplastic lesions formed the major group with 62 (82.7%) cases while 13 (17.3%) were nonneoplastic. The diagnostic accuracy of “squash smears” was found to be 89.2%. “Touch imprints” showed diagnostic accuracy of 78.4%. The low accuracy of touch imprints was attributed to poor cellular yield. The diagnostic accuracy of “frozen section” was 75.7%. However, the overall diagnostic accuracy was 96%.

Conclusion:

We believe that the cytololgical methods and frozen sections are complimentary to each other and both should be used to improve the intraoperative diagnostic accuracy in the CNS lesion.

Intraoperative consultation of central nervous system lesions. Frozen section, cytology or both?

OBJECTIVE

Frozen section is the traditional method of assessing central nervous system (CNS) lesions intraoperatively. Our aim is to determine the diagnostic accuracy of frozen section and/or cytological evaluation of CNS lesions in our center.

STUDY DESIGN

A total of 157 patients with CNS lesions underwent open surgical biopsy or excision in our center during a period of 2 years (2012-2013). All specimens were studied cytologically; of these specimens, 146 cases were also examined by frozen section. Cytology and frozen section slides were studied separately by two general pathologists who were blind to final diagnoses. The final diagnoses were based on permanent sections and IHC studies.

RESULTS

The accuracy rates of frozen section analysis and cytological evaluation were 87% and 86%, respectively. If the two methods were considered together, the accuracy rate improved to about 95%.

CONCLUSIONS

Cytological evaluation is an acceptable alternative to frozen section analysis and also a great supplement to the diagnosis of CNS lesions.

Utilization of frozen sections in the evaluation of chronic epilepsy-related cases

The role of frozen section consultation in the evaluation of chronic epilepsy-associated surgical excisions of brain tissue has not been previously examined. The study retrospectively reviews 335 cases in which a frozen section consultation was obtained in the setting of a resection for chronic epilepsy. In most cases (n = 323), 3 or fewer frozen sections were performed. The most commonly identified pathologies on final diagnosis included tumor or tumorlike lesions (79.1% of cases) and focal cortical dysplasia (20.9% of cases). Frozen section diagnoses discrepant with final diagnoses due to sampling error or misinterpretation were noted in 39 cases and most commonly involved a diagnosis of gliosis or tumor in the setting of a focal cortical dysplasia or diagnosis of gliosis in the setting of a low-grade tumor. In conclusion, frozen section consultation may be particularly useful in the evaluation of neoplasms arising in the setting of chronic epilepsy. Some epilepsy-associated pathology, such as focal cortical dysplasia, may be difficult to diagnose at the time of frozen section and such cases may not be an ideal target for intraoperative frozen section consultation.

Intraoperative neurocytology of primary central nervous system neoplasia: A simplified and practical diagnostic approach

Intraoperative consultations may pose considerable diagnostic challenge to the neuropathologist in diagnosing primary and metastatic neoplasms of the central nervous system (CNS). Cytological preparations in the form of squash, touch, imprint or smears are few of the available modalities in addition to the frozen section (FS). Although the latter is superior in providing both histologic patterns and cytomorphologic details yet smears are of vital importance when tissue available is limited (stereotactic biopsy), scrutinisation of intercellular matrix (astrocytoma versus oligodendroglioma) and evaluation of discohesive cells (lymphoma, pituitary adenoma) and in inflammatory lesions. This review is intended to emphasize the value, applicability and limitations of neurocytology aiming to expedite the intraoperative smear-based diagnoses of CNS neoplasia as per the World Health Organization (WHO) classification. We recommend that whenever possible, both smears and FS should be examined concomitantly and in a correlative manner. In the unlikely event of a mismatch between the findings on smear and FS, intraoperative diagnosis is primarily based on FS, if adequate tissue is available. However, each case must be evaluated on its own merit and in difficult cases relevant differential diagnoses should be offered to facilitate surgical decisions and optimally triage patient management.

Squash preparation: A reliable diagnostic tool in the intraoperative diagnosis of central nervous system tumors

Background:

Intraoperative cytology is an important diagnostic modality improving on the accuracy of the frozen sections. It has shown to play an important role especially in the intraoperative diagnosis of central nervous system tumors.

Aim:

To study the diagnostic accuracy of squash preparation and frozen section (FS) in the intraoperative diagnosis of central nervous system (CNS) tumors.

Materials and Methods:

This prospective study of 114 patients with CNS tumors was conducted over a period of 18 months (September 2004 to February 2006). The cytological preparations were stained by the quick Papanicolaou method. The squash interpretation and FS diagnosis were later compared with the paraffin section diagnosis.

Results:

Of the 114 patients, cytological diagnosis was offered in 96 cases. Eighteen nonneoplastic or noncontributory cases were excluded. Using hematoxylin and eosin-stained histopathology sections as the gold standard, the diagnostic accuracy of cytology was 88.5% (85/96) and the accuracy on FS diagnosis was 90.6% (87/96). Among these cases, gliomas formed the largest category of tumors (55.2%). The cytological accuracy in this group was 84.9% (45/53) and the comparative FS figure was 86.8% (46/53). In cases where the smear and the FS diagnosis did not match, the latter opinion was offered.

Conclusions:

Squash preparation is a reliable, rapid and easy method and can be used as a complement to FS in the intraoperative diagnosis of CNS tumors.

Frozen Section Diagnosis of Pediatric Brain Tumors

Brain tumors represent a significant group of tumors seen in the pediatric population. Intraoperative consultation represents a critical and integral component of the management of these tumors. Since the prevalence, frequency, and location of the different histologic types of brain tumors vary significantly between children and adults, it is reasonable to expect that diagnoses entertained during intraoperative consultation will also differ, influencing the aggressiveness of surgical resection and course of management. It is, therefore, imperative for surgical pathologists responsible for pediatric patients to become familiar with these entities and the diagnostic challenges they pose during the course of surgery.

Image-guided frameless stereotactic biopsy without intraoperative neuropathological examination

OBJECT

Stereotactic biopsy is a safe and effective technique for the diagnosis of brain tumors. The use of intraoperative neuropathological examination has been routinely advocated to increase diagnostic yield, but the procedure lengthens surgical time, may produce false-negative and -positive results, and current biopsy techniques have a very low nondiagnostic rate. Therefore, the authors questioned the need for intraoperative histological evaluation.

METHODS

The authors prospectively studied all patients undergoing image-guided biopsy under the care of a single surgeon (P.L.G.) between July 2005 and October 2007. A Stryker neuronavigation system with a trajectory guide was used to plan a single trajectory, and, using a side-cutting biopsy cannula, multiple biopsy samples were taken from between 1 and 4 sites within the tumor. Tissue was inspected macroscopically by the surgeon and was only submitted for neuropathological assessment postoperatively.

RESULTS

One hundred thirty-four biopsies were performed during the study. A positive diagnosis was established in 133 cases (99.3%). One biopsy was negative (0.7%) and postoperative imaging (performed because the tissue was macroscopically normal) demonstrated inaccurate targeting of the lesion. Significant complications were seen in 3 patients (2.2%) who all had preoperative WHO performance scores of III or IV. Two patients suffered delayed deterioration and died due to probable surgical complications--one with thalamic glioblastoma multiforme (GBM) and one with gliomatosis cerebri. One patient with GBM suffered an intracerebral hematoma that was managed conservatively. Postoperative seizures were seen in 4 patients (3%), and 2 patients (1.5%) experienced a transient neurological deficit. Histological diagnosis showed a GBM in 64 cases, Grade III glioma in 19, Grade I or II in 23, metastasis in 10, lymphoma in 13, and other disease in 4. There were 32 patients discharged to home on the same day as surgery. Compared with the authors' previous retrospective audit into 127 biopsies, this technique showed improved diagnostic yield (99.3 vs 94.5%, p = 0.032) with fewer complications (2.2 vs 4.7% [not statistically significant]).

CONCLUSIONS

This technique of image-guided biopsy has high diagnostic yield with acceptably low morbidity and may be performed as a day case. Intraoperative neuropathological examination would not have increased the diagnostic yield further in this study, and its routine use may not be necessary. In the authors' department pounds sterling 70,350 (UK)/$114,522 (US) would have been saved by not using intraoperative neuropathology in this series. Therefore, intraoperative neuropathology should no longer be routinely recommended.

Frozen section discrepancy in the evaluation of central nervous system tumors

CONTEXT

Frozen section (FS) evaluation of central nervous system (CNS) lesions provides an assessment of specimen adequacy and facilitates triage for ancillary studies. Frozen section also provides an accurate preliminary diagnosis; however, certain lesions are recognized to cause diagnostic challenges at FS.

OBJECTIVE

To identify cases in which there was a discrepancy between the FS diagnosis and final diagnosis in the case to heighten awareness of common diagnostic pitfalls in surgical neuropathology.

DESIGN

All CNS FS cases involving a tumor diagnosis at FS or permanent section (N = 2156) from September 1997 until June 2005 were retrospectively reviewed. Discrepancies between the FS and final diagnoses were identified.

RESULTS

Of the 2156 cases identified, 57 (2.7%) discrepant diagnoses were found. Twelve (21.1%) of 57 discrepancies involved errors in classification of spindle cell lesions, most commonly confusing schwannomas or meningiomas with other lesions. Twelve (21.1%) of 57 cases involved errors in differentiating oligodendrogliomas from astrocytomas. Nine (15.8%) of 57 discrepancies involved errors in the diagnosis of CNS lymphoma. Eight (14.0%) of 57 cases involved errors in differentiating reactive from neoplastic processes, most frequently gliosis versus glioma. Four (7.0%) of 57 discrepancies involved errors in the overgrading of tumors. The remaining 12 (21.1%) of 57 cases included an assortment of other discrepancies.

CONCLUSIONS

Frozen section of CNS neoplastic processes can be highly accurate. Less than 3% of FS diagnoses in 1 institution's experience were discrepant with the final diagnoses. Approximately 80% of the discrepant cases were classified into 5 categories: spindle cell lesions, astrocytoma versus oligodendroglioma, differential diagnosis of CNS lymphoma, reactive versus neoplastic process, and tumor overgrading. Awareness of these pitfalls may help in further increasing diagnostic accuracy.

Intraoperative cytological evaluation of Marjolin ulcers

BACKGROUND

Marjolin ulcers are malignant neoplasia developing in chronic open wounds and pathological scars. A definitive diagnosis is made by histological examination of permanent sections. Frozen section biopsy has been widely used for intraoperative diagnosis and evaluation of surgical excision safety margins. This preliminary study aims to discuss the reliability of a simpler and faster method -- intraoperative cytology -- in the diagnosis of Marjolin ulcers.

PATIENTS AND METHODS

Touch or scrape smears of 76 Marjolin ulcers from 22 patients were assessed, and features were compared to the histological appearance of permanent sections.

RESULTS

Cytology revealed squamous cell carcinoma (SCC) in 45 ulcers from 11 patients. Histology confirmed SCC in 48 ulcers from 12 patients. No false-positive and one false-negative results were found. Cytology was found to have a 98.7% accuracy, 98% sensitivity and 100% specificity in the intraoperative diagnosis of Marjolin ulcers.

CONCLUSIONS

Cytology is a fast and reliable alternative in the intraoperative diagnosis of Marjolin ulcers.

Intraoperative Consultation in the Diagnosis of Pediatric Brain Tumors

Context.—The prevalence of brain tumors in the pediatric population differs from that in the adult population. Similarly, the frequency and location of the different histologic types of brain tumors vary significantly between the pediatric and adult populations.

Objective.—To familiarize the pathologist with the pediatric brain tumors encountered during intraoperative consultation and with the appropriate differential diagnoses in this setting.

Data Sources.—The medical literature and the author's experience and expertise.

Conclusion.—Compared with adult brain tumors, pediatric brain tumors present different challenges and distinct differential diagnoses that the pathologist should be aware of during intraoperative consultation.

Intraoperative Consultation, Cytologic Preparations, and Frozen Section in the Central Nervous System

Context.—Intraoperative evaluation of lesions in the central nervous system requires the correlation of clinical, radiologic, and histologic data and knowledge of clinicopathologic entities and their common locations. Advances in neuroimaging during the last 20 years have revolutionized the diagnosis and treatment of central nervous system diseases. The diagnosis and treatment of patients have improved because of these changes and have allowed access to regions that were previously inaccessible. These new approaches have placed the pathologist in a key role in the diagnosis and treatment of patients with central nervous system lesions. Assessment of the adequacy of the material, particularly for stereotactic biopsies, is necessary, and a combination of cytologic imprint preparations and frozen sections are often used. This review discusses many of the issues involved in intraoperative consultation and provides a simplified approach to the differential diagnosis of a variety of central nervous system lesions that may be encountered intraoperatively.

Objective.—To provide guidelines for and address potential pitfalls in the intraoperative management of the central nervous system.

Data Sources.—Author's experience and pertinent literature.

Conclusions.—Careful assessment of the gross specimen coupled with prudent use of frozen sections and cytologic imprint preparations is pivotal to reducing intraoperative error rates and preventing needless anxiety for the patient.