From smear to diagnosis: the impact of ancillary techniques in lymph node fine-needle cytology

Introduction: The diagnostic accuracy of lymph node fine-needle aspiration cytology (LN-FNAC) relies on proper management of the diagnostic material and on ancillary techniques (AT). Despite the recognized utility of AT in LN-FNAC, their specific role on diagnostic accuracy remains underexplored. This study aims to analyze the impact of AT on the diagnostic accuracy of LN-FNAC. Materials and methods: A retrospective review of 452 LN-FNAC samples (2021–2024; University Hospital of Salerno) was performed, identifying 187 cases in which AT were applied. Each case was classified according to the Sydney/WHO system. The impact of AT was assessed both on the first diagnostic level (L1 = inadequate/nondiagnostic, L2 = benign, L3 = atypical, L4 = suspicious for malignancy, and L5 = malignant) and on the second diagnostic level (specific diagnostic entity). Results: Regarding the first level, the number of L3 and L4 diagnoses was reduced by the application of AT: n = 67/71 (94%) L3 cases were reclassified as L2 or L5; n = 26/26 (100%) L4 cases were reclassified as L5. Regarding the second level, it was reached only in 32/187 (17%) cases without AT and in 125/187 (67%) cases with AT. Finally, AT supported 19.8% of diagnoses, enhanced 36.4%, enabled 38.0%, and was noncontributory in only 5.9% of cases. Conclusions: This study shows that AT impacted on both the first and second level of the Sydney/WHO system and it had a positive impact on diagnoses in a significant proportion of cases. These findings highlight not only the importance of AT for LN-FNAC, but also the impact of strategic material management and the appropriate AT selection in achieving accurate diagnoses.