Thyroid Fine Needle Aspiration of Nodules ≥ 4 cm: Cytologic Outcomes and Risk Stratification in a Tertiary Centre

ABSTRACT Objectives To assess cytologic outcomes of thyroid nodules ≥ 4 cm undergoing FNA and compare malignancy risk between nodules that underwent an FNA by TIRADS criteria versus size alone. Methods A retrospective review of thyroid FNAs from January 2012 to August 2025 was conducted. Nodules ≥ 4 cm were included, with data extracted from RIS and pathology records. Age, gender, nodule size, TIRADS, FNA indication, and Bethesda category were recorded. Cytology was grouped into benign/non‐diagnostic (Bethesda I–II) versus indeterminate/malignant (Bethesda III–VI). The Bethesda classification (I–VI) corresponds to increasing malignancy risk. Statistical analysis used a chi‐square test ( p < 0.05 considered significant). Results Four hundred and eighty‐six nodules ≥ 4 cm underwent FNA (104 size‐only; 382 TIRADS‐based). Size‐only group: 13 Bethesda I, 79 Bethesda II, 11 Bethesda III, 1 Bethesda IV (11.5% indeterminate/malignant). TIRADS group: 37 Bethesda I, 266 Bethesda II, 55 Bethesda III, 18 Bethesda IV, 5 Bethesda V, 1 Bethesda VI (20.7% indeterminate/malignant). Chi‐square = 3.91 ( p = 0.048). Conclusion While size alone was not a strong predictor of malignancy, combining TIRADS classification improved detection. As > 10% of large nodules without suspicious features were Bethesda III or higher, FNA is recommended for all nodules ≥ 4 cm to minimise missed malignancies.