Application of Sydney System for Lymph Node Cytology at a Tertiary Care Centre in Central India

Fine-needle aspiration cytology (FNAC) of a lymph node has become a reliable and well-accepted first-level diagnostic technique due to its minimally invasive nature, rapid turnaround time, and low cost. The lack of standard guidelines and the question of how it can provide diagnostic information have reduced its acceptance. The Sydney system for lymph node cytology provides a comprehensive standardized approach to lymph node FNA. In our study, we have introduced the Sydney system for performance, classification, and reporting of lymph node FNAC at a tertiary care center and correlated it with the histopathological diagnosis wherever available.

All lymph node aspiration done at our institute from January 2014 to April 2023 (n = 647) with and without histopathological reports were obtained and the Sydney category was assigned accordingly. The study was ambispective. The retrospective cases (n = 471) were reclassified according to the Sydney system and 176 cases were performed and reported as per the Sydney system.

In the present study, 647 LN FNAC cases were included and categorized according to the Sydney system of reporting LN FNAC. Among them, 46/647 (7.1%) cases were categorized into the Inadequate category, 367/647 (56.7%) into the Benign category, 23/647 (3.5%) cases into the Atypia of undetermined significance/Atypical lymphoid cells of undetermined significance category, 36/647 (5.5%) cases into the Suspicious of Malignancy category, and 175/647 (27%) cases into the Malignant category. One hundred and thirty-six cases were histopathologically examined. The sensitivity, specificity, PPV, NPV, and diagnostic accuracy in these categories were 98.7%, 97.9%, 98.7%, 97.9%, and 98.4%. Risk of malignancy (ROM) was 100% in Category I, 2.1% in Category II, 75% in Category III, 95.4% in Category IV, and 100% in Category V.

Adoption of the Sydney system, by the introduction of standardized categorization, may improve the LN FNAC diagnostic accuracy. The tiered risk stratification classification scheme, as proposed by the Sydney system, may prove helpful in risk stratification and effectively guiding the clinical management of patients with lymphadenopathy.