Structured Reporting of Lymph Node Cytopathology using the 2020 Sydney System Guidelines-A Retrospective Study

Abstract

Introduction: Fine Needle Aspiration Cytology (FNAC) is a valuable diagnostic aid for evaluation of lymph node pathology. The new Sydney System (2020) for classification and reporting of lymph node FNAC has put forth guidelines for a categorical classification using uniform terminology and morphologic criteria, a major step towards standardisation. Aim: The study was aimed to evaluate cytopathology of lymph node lesions during 2 year period by applying the proposed Sydney system and to assess the category wise Risk Of Malignancy (ROM) by comparing with histopathology diagnosis in available cases. Materials and Methods: A retrospective observational study was conducted in 2021 December, on lymph node aspirates obtained during two-year period from January 2018 till January 2020 in the department of Pathology of a tertiary care centre. FNAC of 250 lymph node aspirates were evaluated. Smears were reviewed and categorised as per the Sydney System of reporting as, L1: non diagnostic/inadequate, L2: benign, L3: atypical cells/atypical lymphoid cells of undetermined significance, L4: suspicious for malignancy, L5: malignant. The diagnostic accuracy of cytology and ROM in each category was assessed comparing with the gold standard histopathology diagnosis where available. Results: Category wise distribution of 250 cytological diagnosis of lymphadenopathy reclassified in Sydney system were L1-14 (5.60%); L2-159 (63.60%); L3-04 (1.60%); L4-05 (2%); and L5-68 (27.20%) cases. Using histopathology as gold standard available in 53 cases, the ROM in each category was found to be 0%, 3%, 66.66%, 100% and 100%, respectively. The sensitivity, specificity, Positive Predictive Value (PPV), Negative Predictive Value (NPV) and diagnostic accuracy of cytological diagnosis was found to be 95.65%, 96.29%, 95.65%, 96.29% and 96%, respectively. Reactive lymphadenitis in 86 (34.40%) and metastatic carcinoma in 61 (24.40%) cases were the most common benign and malignant lesions respectively. Conclusion: The Sydney system of structured reporting in lymph node cytology provides a clear-cut terminology, uniformity, and reproducibility of reports. It enhances the role of FNAC by alerting the clinician for follow-up and ancillary studies in atypical and equivocal cases. In the non diagnostic L1 category, repeat procedure or biopsy should be recommended to avoid False Negative (FN) diagnosis.