Reclassification Of Lymph Node FNAC Cases Using the Sydney System: A Descriptive Study at Chughtai Institute of Pathology

Abstract

Background:

Fine needle aspiration cytology (FNAC) is a commonly used, least-invasive method of assessing abnormalities of lymph nodes. Its clinical usefulness has been limited by a large margin of uniform reporting terminology, and this leads to inability to interpret and manage uniformly. The Sydney System, which is suggested as a five-tiered classification framework (L15), provides a structured method similar to that in use in thyroid and salivary gland cytopathology.

Objective:

To determine the utility of the Sydney System in re-classification of FNAC cases of lymph node and to determine the prevalence of diagnostic categories, and a study of the discrepancy rates between cytological and clinical diagnoses.

Methods:

The research was a descriptive study done at Chughtai Institute of Pathology in a period of one year after institutional review board approval. FNAC of lymph nodes (n=341), was retrospectively revisited and reorganized based on the categories of Sydney System: L1 (non-diagnostic), L2. The Benign, Atypical cells of undetermined significance, Suspicious of malignancy, and Suspicious of benignity (Malignant). Discrepancies between cytological classification and available clinical/histopathological data were also evaluated.

Results:

Of 341 cases, the Sydney System distribution was as follows: L1 (non-diagnostic): 40 cases (11.7%), L2 (Benign): 224 cases (65.7%), L3 (Atypical/undetermined significance): 7 cases (2.1%), L4 (Suspicious for malignancy): 1 case (0.3%), and L5 (Malignant): 69 cases (20.2%). Among L2 cases, the most common diagnosis was tuberculosis/granulomatous lymphadenitis (29%), followed by miscellaneous benign conditions (57%) and reactive lymph nodes (14%). Among L5 cases, metastatic carcinoma accounted for 91% and lymphoma for 9%. Discrepancies between cytological classification and clinical outcome were identified in 27 cases (7.9%), with major discrepancies in 3 cases (37.5% of discrepant cases) and minor discrepancies in 5 cases (62.5% of discrepant cases).

Conclusion:

The Sydney System provides a practical, reproducible framework for reporting lymph node FNAC. Its implementation at Chughtai Institute of Pathology demonstrated a high benign case rate with a meaningful proportion of malignant diagnoses, confirming the system's clinical applicability in a high-volume, resource-rich pathology setting.