Abstract
Introduction Evaluation of intraoperative squash smear and frozen section (FS) in central nervous
system (CNS) neoplasms is consistently practiced for rapid assessment and has several
advantages to its credence. It is an invaluable tool to ensure adequacy of tissue
obtained to establish the diagnosis. Moreover, it aids in guiding the surgeon for
critical decisions regarding the extent of resection. Although molecular markers have
been integrated with morphology in the revised 2016 World Health Organization classification
of brain tumors, precise morphological assessment still remains the foundation for
the diagnosis and rapid intraoperative assessment of morphological details is equally
critical and rewarding.
Objective This study aims to audit the diagnostic disparity between intraoperative diagnoses
based on a combination of squash cytology and FS in cases of CNS lesions with gold
standard, final diagnosis based on examination of formalin fixed paraffin embedded
hematoxylin, and eosin-stained tissue sections.
Materials and Methods All intraoperative squash cytology and FS reported for CNS lesions from January 2017
to December 2020 were reviewed. The cases were categorized into three groups—group
1: when diagnosis of intraoperative diagnosis based on a combination of squash cytology
and FS was same as the final histopathological diagnosis (concordant), group 2: partially
concordant, and group 3: discordant cases.
Statistical Analysis Descriptive statistics was used to classify the data and diagnostic accuracy was
calculated.
Results Complete concordance was present in 69.96% (191/273) cases, 20.1% (55/273) cases
showed partial concordance, and 9.89% (27/273) cases were discordant with histopathological
diagnosis. Out of the 27 discordant cases, misclassification of tumor type was the
most common category (11 cases, 40%), followed by grading mismatch (7 cases, 25.9%),
and misdiagnosis of tumor versus nontumor conditions (9 cases, 33.3%).
Conclusion Our study shows that combination of intraoperative squash cytology and FS shows a
high percentage of accuracy in arriving at intraoperative diagnosis in cases of intracranial
lesions. Regular audits of discordant cases should be conducted by surgeons and pathologists
as part of a quality assurance measure to sensitize themselves with the potential
pitfalls, minimizing misinterpretation and helping in providing a more conclusive
opinion to the operating surgeons.
Keywords frozen section - squash smear - central nervous system - intraoperative diagnosis
