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ORIGINAL ARTICLE
Year : 2022  |  Volume : 11  |  Issue : 3  |  Page : 181-185

Study of intraoperative squash cytology and frozen section diagnosis of central nervous system lesions with histopathological correlation


Department of Pathology, Dr. Pinnamanaeni Institute of Medical Sciences and Research Foundation, Andhra Pradesh, India

Date of Submission12-May-2021
Date of Acceptance13-May-2021
Date of Web Publication26-Dec-2022

Correspondence Address:
Dr. Sruthi Nannapaneni
4-13-9, Nannapaneni Street, Ithanagar, Tenali, Andhra Pradesh
India
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/jdrntruhs.jdrntruhs_51_21

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  Abstract 


Context: Intraoperative evaluation of central nervous system (CNS) lesions helps to guide the management by providing preliminary diagnosis, confirming the presence or absence of a neoplasm. Squash cytology and frozen section are reliable and sensitive techniques for rapid intraoperative diagnosis. However, both have respective limitations and the choice of the technique depends on individual preference and tissue availability.
Aims: This study aims to determine the diagnostic accuracy of intraoperative squash cytology and frozen section diagnosis by correlating with the final histopathological diagnosis.
Settings and Design: Prospective study over a span of 2 years in a tertiary care center.
Materials and Methods: A total of 64 cases were subjected to intraoperative squash cytology and frozen section study and the intraoperative diagnosis was compared with final histopathological diagnosis.
Statistical Analysis Used: Diagnostic accuracy, sensitivity, specificity, positive predictive value, and negative predictive value.
Results: Out of the 64 cases, 86% cases were neoplastic and 14% cases were non-neoplastic. The overall diagnostic accuracy of squash cytology was 90.6% and frozen section was 93.7%.
Conclusion: Squash cytology and frozen section are highly accurate and reliable techniques for intraoperative frozen section evaluation of CNS lesions. However, both the techniques have respective limitations. When combined together they help improve the overall diagnostic accuracy.

Keywords: Central nervous system lesions, frozen section, intraoperative diagnosis, squash cytology


How to cite this article:
Kadiyala P, Nannapaneni S, Murari A, Vallabhaneni KC, Damera NC, Diddi RR. Study of intraoperative squash cytology and frozen section diagnosis of central nervous system lesions with histopathological correlation. J NTR Univ Health Sci 2022;11:181-5

How to cite this URL:
Kadiyala P, Nannapaneni S, Murari A, Vallabhaneni KC, Damera NC, Diddi RR. Study of intraoperative squash cytology and frozen section diagnosis of central nervous system lesions with histopathological correlation. J NTR Univ Health Sci [serial online] 2022 [cited 2023 Jan 27];11:181-5. Available from: https://www.jdrntruhs.org/text.asp?2022/11/3/181/365023




  Introduction Top


Intracranial lesions account up to 5–10 per 100,000 population and make up two percent of all malignancies in a developing country like India.[1]

Though preoperative neurodiagnostic imaging provides the clinician with detailed information, its images are sometimes inaccurate and an explicit diagnosis regarding the nature of the lesion is based on histological confirmation.[2]

Since preoperative histopathological diagnosis is not possible in central nervous system (CNS) lesions, a rapid intraoperative diagnosis helps the neurosurgeon make critical decisions regarding modifying the approach and to decide on further plan of management.[3]

The main techniques for evaluation of intraoperative biopsies include squash cytology and frozen section.[4]

Preparation of smears from brain biopsies has been first described by Eisenhardt and Cushing in the 1930s. The frozen section procedure practiced today is based on description by Dr. Louis. B. Wilson in 1905.[5]

Intraoperative squash cytology is rapid, inexpensive, and technically unchallenging. The soft consistency of CNS lesions aids in smear preparation and reveals superb cytological detail.[6],[7]

Frozen section provides good morphological detail and histological typing; however, it needs expensive equipment and is technically challenging.[8]

The aim of this study is to evaluate the intraoperative squash cytology and frozen section diagnosis and determine their accuracy by correlating with the final histopathological diagnosis.


  Materials and Methods Top


Study design

This is an observational prospective study.

Inclusion criteria

All neurosurgical specimens sent for intraoperative evaluation were included in the study.

Exclusion criteria

  • Biopsies which are very tiny to be processed for both squash cytology and frozen section.
  • Biopsies with inconclusive diagnosis on squash cytology or frozen sections.


A total of 64 cases were included in the study. Detailed clinical history along with radiological reports was available during the time of diagnosis.

Immediately after receiving the specimen, the gross characteristics were noted and a representative sample was taken for squash cytology and frozen section.

A squash smear is prepared by placing small tissue fragment on a labeled glass slide, which was gently crushed with a second slide held at a right angle. This slide was gently rotated to spread the specimen evenly across the base of the labeled slide. The slides were immediately fixed in 95% ethyl alcohol and stained with rapid hematoxylin and eosin [H and E].

For the frozen sections, approximately 1 × 1 cm tissue section from the specimen is sampled and embedded in optimal cooling temperature compound, which is rapidly frozen in the cryostat chamber up to −20°C. 5-μm thick sections are cut and retrieved on a glass slide and immediately fixed in 10% formalin which are stained with rapid H and E.

The stained slides are evaluated and an intraoperative diagnosis is established using WHO classification and grading system.[9]

Squash cytology and frozen section diagnoses were correlated with the final histopathological diagnosis and categorized into three groups.[10]

Complete correlation was considered when intraoperative squash cytology/frozen section diagnosis was found identical to the final histopathological diagnosis. Partial correlation was considered when there was ±1 grade of deviation in tumor grading. When the intraoperative diagnosis was not confirmed by the final histopathology, it is noted as no correlation. Institutional ethics committee approval was taken prior to the study on 17/12/20.


  Results Top


A total of 64 cases which have been sent for intraoperative diagnosis have been analyzed.

The age distribution ranges from 2–82 years, with a mean age of 43 years.

Majority of the patients, 75%, were above 40 years old, 17% between 20 and 40 years, and 8% less than 20 years old.

There is a slight female predominance (35/64) compared to males (29/64) with M:F ratio of 1:1.2. 86% of the cases were neoplastic and 14% cases were non-neoplastic. 83% of the cases were located in the cerebral hemispheres with fronto-temporal region being the most common location followed by 17% of cases in the spine.

Among the neoplastic lesions, glial tumors constitute 31%, followed by meningiomas 20%. Granulomatous lesions constitute 13% of the cases.

Squash cytology showed complete correlation with final histopathology diagnosis in 82% cases and partial correlation in 9% cases and no correlation in 9% cases.

Frozen section showed complete correlation with final histopathology diagnosis in 85% cases and partial correlation in 7.5% and no correlation in 7.5%.

In correlation with final histopathology, the overall diagnostic accuracy of squash cytology was 91% and frozen section was 92%.

The sensitivity, specificity, PPV, and NPV of squash cytology in identifying a neoplastic condition were 100%, 70%, 92.7%, and 100% and, for frozen section, they were 100%, 75%, 94.5%, and 100%.


  Discussion Top


Intraoperative diagnosis of CNS lesions is of utmost importance and helps the neurosurgeon make critical decisions. Radiological investigations have revolutionized the diagnosis and management of CNS tumors; however, histopathological diagnosis remains definite for identification and grading of the tumor. The knowledge of location, clinical presentation, and radiological correlation helps the pathologist in forming a realistic differential diagnosis.[11]

The ideal intraoperative diagnostic method should be accurate, rapid, and should allow for preservation of tissue.[12]

Frozen sections provide good morphological details and histologic typing; however, the inherent soft and edematous nature of neurosurgical specimens leads to ice crystal formation, freezing artefacts resulting in inferior cytological detail.[13]

Firm and rubbery lesions such as meningiomas, schwannomas, ependymomas, metastatic lesions, and inflammatory lesions are better visualized on frozen sections.[14]

Softer and friable lesions such as astrocytomas, oligodendrogliomas, and pituitary adenomas smear easily and are better visualized in squash cytology.[15]

In the present study, 64 cases were analyzed and the data was compared with other studies.

Out of the total cases, 75% of the cases were in the age group above 40 years, 17% between 20 and 40 years, and 8% less than 20 years of age. Similar demographic findings were reported in studies by Savargaonkar and Farmer[6], Verma et al.,[7] and Govindaraman et al.[16]

There was a slight female predominance in the present study with M:F ratio of 1:1.2. Similar findings were reported by Govindaraman et al. and Patil et al.[16],[17]

Majority of the cases 83% were intracranial with frontal lobe being the most common location followed by temporal lobe and 17% cases were intraspinal. Similar findings were reported by Jha et al.[18] (85.7% intracranial and 7.3% intraspinal).

In the present study, 86% of the cases were neoplastic and 14% were non-neoplastic. Similar findings were reported by Nanarng et al.[12] where it was 82.7% neoplastic and 17.3% non-neoplastic.

Histomorphological spectrum of CNS lesions is outlined in [Table 1]. The most commonly encountered lesions were gliomas followed by meningiomas, similar findings were reported by Rao et al.[19] Granulomatous lesions can be sometimes difficult to diagnose on squash cytology and necrotic material adheres poorly on the slides.[20]
Table 1: Histomorphological spectrum of CNS lesions and intraoperative squash cytology and frozen section correlation

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In the present study, the overall diagnostic accuracy of squash cytology was 91%, whereas for frozen section, it was 92.5%. It is comparable with similar studies as outlined in [Table 2].[13],[21],[22],[23]
Table 2: Diagnostic accuracy of intraoperative squash cytology and frozen section when compared with similar studies

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The diagnostic accuracy of squash cytology was 82% when only complete correlation was considered, whereas it was 91% when both complete and partial correlations were considered. Frozen section showed a diagnostic accuracy of 86% with complete correlation, which increased up to 92.5% when both complete and partial correlations were considered.

Among the cases that showed no correlations, majority were gliomas followed by meningiomas and metastatic lesions.

Two cases of gliomas were diagnosed as low grade gliomas in both squash cytology and frozen section, whereas on histopathology, they were diagnosed as reactive gliosis. Oneson et al. in their study reported that the most common diagnostic difficulty was to differentiate glioma from reactive gliosis.[24] Histological features such as low cellularity and low nuclear cytoplasmic ratio favor reactive gliosis, whereas high cellularity, atypical mitosis, and microcystic spaces are observed in gliomas.[23]

Further diagnostic difficulty was observed in differentiating meningiomas from schwannomas which commonly arise at the cerebellopontine angle. Meningiomas and schwannomas are firm tumors and yield poor cellularity on squash cytology.[3],[25]

Frozen sections provide best architectural features to diagnose meningiomas. However, Burger and Vogel[26] reported that some meningiomas lack whorling, psammoma bodies, and cytoplasmic protrusions, features which are typically used for their diagnosis.

In squash cytology, length to breath ratio of nucleus can be used to differentiate between meningiomas and schwannomas. Kobayashi[27] suggested that in schwannomas, the length to breath ratio of nucleus is greater than two, whereas in meningiomas, it is usually less than two.

One case of metastasis was diagnosed as Grade IV astrocytoma. Nanarng et al.[6],[12],[16] reported similar diagnostic difficulty in differentiating metastatic carcinoma from glioblastoma multiforme. Metastatic carcinomas lack the fibrillary background and show cells with abundant dense cytoplasm.[12],[28]

Powell[4] states that squamous and adenocarcinomatous deposits are best picked up on frozen sections.

The sensitivity and specificity of squash cytology in detecting a neoplastic lesion were 100% and 70% which were comparable with Samal et al.[21] (94.4% and 85.7%), Bhardwaj et al.[29] (97.2% and 100%), and Sanjeev et al. (94.7% and 95.6%).[30]

In frozen section study, detecting a neoplastic lesion had a sensitivity and specificity of 100% and 75% which was comparable with Samal et al.[21] (96% and 75%) and Din et al.[25] (94.8% and 87.5%).


  Conclusion Top


Intraoperative diagnosis of CNS lesions is of utmost importance. Squash cytology is rapid and inexpensive technique and provides good cytological detail. Frozen sections provide better morphological pattern, but limited by freezing artefacts, especially in CNS lesions. In our study, the diagnostic accuracy of both frozen section and squash cytology are comparable with each other. In combination squash cytology and frozen section diagnosis complement each other and improve the overall diagnostic accuracy.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.



 
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