Background: Fine-needle aspiration cytology (FNAC) is a reliable technique that has been used for many years in lymphadenopathy diagnosis. Although conventional smear is the standard approach in FNAC, liquid-based cytology (LBC) is accepted as an alternative method. Reporting standardization is a significant gap in fine-needle aspiration cytology, leading to failure in pathologist-clinician dialog and interobserver variability. In 2020, an expert panel proposed the Sydney system for classifying and reporting lymph node aspiration cytology. This study aimed to evaluate the diagnostic accuracy of LBC in lymph node aspiration cytology under the guidance of the Sydney system.
Methods: Five hundred-four LBC samples were reevaluated and classified according to the Sydney system. Of these, n = 24 were categorized as L1-inadequate/non-diagnostic, n = 283 as L2-benign, n = 36 as L3- atypical cells of undetermined significance/atypical lymphoid cells of uncertain significance (AUS/ALUS), n = 48 as L4-suspicious, and n = 113 as L5-malignant. Four hundred-one samples were histopathologically confirmed. The diagnostic accuracy of LBC and the risk of malignancy for each Sydney category were calculated.
Results: The results were as follows: sensitivity 98.97%; specificity 98.60%; positive predictive value 94.80%; negative predictive value 99.29%; and overall diagnostic accuracy 98.75%. The ROM was 16.6% for L1, 0.7% for L2, 88.8% for L3, and 100% for L4 and L5.
Conclusion: LBC is suitable for use in lymph node aspiration under the guidance of the Sydney system and has high diagnostic accuracy. Future comprehensive studies will increase the applicability of the Sydney system and minimize interobserver variability.
Keywords: Sydney system; cytology; fine-needle aspiration; lymph node.
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