Supplementary Material for: Adequacy assessment in lymph node aspirates – an exploratory cytomorphologic analysis of negative cervical node aspirates of head and neck carcinomas

Introduction Fine needle aspiration cytology (FNAC) of lymph node is sensitive for detection of metastatic carcinoma but not without a significant false negative rate. This study reviews clinicocytological features of negative node aspirates to identify predictive factors for establishing adequacy criteria. Methods Negative FNAC specimens matched with neck dissection from a primary diagnosis of head and neck squamous cell, or undifferentiated (nasopharyngeal) carcinoma were reviewed for clinical and cytological parameters including lymphoid, inflammatory, and background components. Results Slides from 86 lymph node aspirates including 50 positive for metastasis on follow-up were retrieved. Higher total lymphocyte count, lymphoid fragment count, germinal center fragment count, undifferentiated histology, presence of histiocytes and absence of blood were associated with a true negative cytologic diagnosis (p0.05). Undifferentiated histology, small lymphoid and germinal center fragments were independent factors indicative of a true negative diagnosis (p10 small lymphoid, >20 large lymphoid and >2 germinal center fragment per five HPFs as optimal adequacy thresholds. Stricter total lymphocyte count cutoff accompanies increase of diagnostic accuracy, up to 0.67 for ≥5 HPFs with >500 lymphocytes. Conclusion Total counts of lymphoid and germinal center fragments from multiple HPFs are useful in adequacy assessment of lymph node aspirates and improves diagnostic performance of FNAC in exclusion of metastatic carcinoma.