Assessment of Interobserver Variability and Cytomorphological Analysis in Lymph Node FNAC: A Comparative Study of Conventional and Sydney Systems

Background: Fine Needle Aspiration Cytology (FNAC) plays a vital role in the initial evaluation of lymphadenopathy. However, the absence of a standardized reporting system has led to variability in diagnosis. The Sydney system was recently proposed to address this issue by providing structured criteria for lymph node cytology reporting. The objective is to assess and compare interobserver variability and cytomorphological interpretation of lymph node FNAC using the conventional system and the Sydney system of reporting. Material and Methods: An observational study was conducted on 150 cases of lymph node FNACs with available histopathological correlation. Each case was evaluated and categorized independently by three primary investigators and two blinded pathologists using both the conventional and Sydney systems. Cytomorphological parameters were documented, and interobserver agreement was statistically analyzed using kappa values. Results: The Sydney system demonstrated improved reproducibility among pathologists compared to the conventional system. Kappa values for interobserver agreement were significantly higher with the Sydney system, particularly in borderline and indeterminate categories. The structured format and defined criteria of the Sydney system contributed to reduced ambiguity in reporting. Conclusion: The Sydney system improves interobserver consistency and offers a more standardized approach to lymph node cytology reporting. Its adoption in routine pathology practice can enhance diagnostic communication and potentially reduce diagnostic errors.

Keywords: FNAC, lymph node, interobserver variability, Sydney system, diagnostic consistency, cytopathology.