Lymph Node Cytopathology Reporting Based on the 2020 Sydney System Guidelines: Correlation Between Histopathology and Cytology

Abstract

Introduction: Fine Needle Aspiration Cytology (FNAC) is a useful method for diagnosing lymph node pathology. The updated Sydney System (2020) provides clear guidelines for categorizing and reporting FNAC results, promoting uniformity in terminology and criteria. This standardization is a significant step forward in lymph node pathology diagnosis. FNAC is a straightforward technique for diagnosing and assessing lymphadenopathies, but the presence of numerous conditions and cytomorphological similarities can complicate the diagnosis. This study aims to analyze lymph node cytopathology reports following the 2020 Sydney System guidelines and compare them with histopathological findings.

Aim: The study assessed lymph node lesions using the Sydney system over 18 months and calculated the Risk of Malignancy (ROM) for each category by comparing it with histopathology diagnoses in available cases.

Materials and Methods: An observational study was conducted from January 2022 to June 2023 at a tertiary care center's Pathology department. The study analyzed 260 lymph node aspirates collected over a one-and-a-half-year period using fine-needle aspiration cytology (FNAC). The aspirates were classified based on the Sydney System into five categories: L1 - non-diagnostic/inadequate, L2 - benign, L3 - atypical cells/atypical lymphoid cells of undetermined significance, L4 - suspicious for malignancy, and L5 - malignant. The accuracy of cytology and ROM was evaluated by comparing them to histopathology, the gold standard diagnosis.

Results: Distribution of 260 cytological diagnoses of lymphadenopathy classified in the Sydney system by category were as follows: L1-16 (6.00%); L2-161 (62.00%); L3-06 (2.30%); L4-07 (2.70%); and L5-70 (27.00%) cases. Histopathology was considered the gold standard in 53 cases, revealing malignancy rates (ROM) of 0%, 3%, 66.66%, 100%, and 100% in each category. Cytological diagnosis showed a sensitivity of 95.65%, specificity of 96.29%, Positive Predictive Value (PPV) of 95.65%, Negative Predictive Value (NPV) of 96.29%, and diagnostic accuracy of 96%. Reactive lymphadenitis was the most common benign lesion in 88 (33.85%) cases, while metastatic carcinoma was the most common malignant lesion in 63 (24.30%) cases.

Conclusion: The Sydney system for lymph node cytology reporting ensures standardized terminology and reproducibility in reports. It helps guide clinicians on follow-up and ancillary studies in atypical and equivocal cases. In cases classified as non-diagnostic (L1), a repeat procedure or biopsy is recommended to prevent false negative diagnoses.