Bridging Cytology and Histology: Concordance Analysis of Lymph Node Lesions within the Sydney Framework

Benign and malignant lymphadenopathy is a common presenting feature in a wide spectrum of diseases. Previously, there was no standard reporting system or common terminology available for lymph node cytology. A diagnostic "gray zone" exists in lymph node cytology, where accuracy declines, making it difficult to categorize certain lesions and leading to diagnostic discrepancies. The aim of the study was to assess the accuracy of fine needle aspiration of the lymph nodes and critically evaluate the cytohistological discordant cases. In the 20th International Congress of Cytology held in Sydney in 2019, a standardized category-based lymph node cytology reporting system was proposed.

This is a retrospective study conducted at the Department of Cytopathology from January 2021 to December 2025. A total of 1500 cases were re-evaluated and reviewed and were classified according to the Sydney System and compared with clinical and histopathological diagnoses. The present study aimed to analyze and classify lymph node samples as per the newly proposed Sydney System and to calculate risk of malignancy, sensitivity, specificity, positive predictive value, and negative predictive value (NPV) for all categories, considering histopathology as the reference standard. The statistical analysis was performed using SPSS version 20.

Of the 1500 cases, distribution was as follows: L1, 150; L2, 1000; L3, 180; L4, 115; and L5, 55. Risk of malignancy (ROM) was 1.3% for L1, 0.7% for L2, 99.4% for L3, 99.1% for L4, and 96.36% for L5.

The Sydney System study helped in achieving uniformity and reproducibility of cytological diagnosis. It enhanced understanding and communication between clinicians and pathologists, thereby improving patient care.