Investigation of various factors for discriminating between cytologic diagnosis of "atypical" versus "suspicious" in fine needle aspiration biopsy of head and neck lymph nodes.

INTRODUCTION: "Atypical" (ATY) and "suspicious for malignancy" (SUS) diagnostic categories are associated with the highest rate of interobserver variability in all classification systems due to lack of consensus for objective and reproducible criteria for each category. We investigated possible factors that may prompt ATY versus SUS diagnoses in head and neck lymph node cytology.

MATERIALS AND METHODS: Patients with ATY or SUS diagnosis on head and neck lymph node fine needle aspiration biopsy between 2020 and 2023 were evaluated. Health records and archival slides were reviewed to document 22 variables for each case. Risk of malignancy for both categories was calculated. Cases were analyzed based on whether cytologic evaluation suggested a hematologic neoplasm.

RESULTS: A total of 118 cases were included. Risk of malignancy differences for ATY versus SUS were striking and statistically significant (P < 0.0001). In hematologic cases, presence of concurrent biopsy and proportion of abnormal population by flow cytometry were significantly different between ATY versus SUS cases (P = 0.031 and P = 0.037, respectively). In nonhematologic cases, clinical concern and presence of abnormal ancillary tests showed statistically significant differences between ATY versus SUS cases (P = 0.004 and P = 0.028, respectively).

CONCLUSIONS: Cytopathologists are very skilled at visually discerning levels of concern for malignancy. Proportion of abnormal cells detected by flow cytometry was higher in SUS versus ATY in hematologic cases, and presence of abnormal ancillary tests was higher in SUS versus ATY in nonhematologic cases. Further studies are needed to understand and refine employment of the proposed diagnostic categories to maximize the clinical utility of lymph node fine needle aspiration.