Background <p>Papillary thyroid carcinoma (PTC) frequently metastasizes to cervical lymph nodes, and accurate detection of metastasis is essential for optimal treatment planning. While fine-needle aspiration cytology (FNAC) is a common diagnostic tool, its sensitivity can be limited in certain cases. Measuring thyroglobulin (Tg) levels in fine-needle aspiration washout (FNAB-Tg) fluids may enhance diagnostic accuracy.</p> Aims <p>To evaluate the diagnostic performance and optimal cut-off value of thyroglobulin (Tg) measurement in fine-needle aspiration washout (FNAB-Tg) of cervical lymph nodes, and to compare its diagnostic accuracy with FNAC in detecting metastatic lymph nodes in PTC.</p> Methods <p>Fine-needle aspiration (FNA) was performed on cervical lymph nodes in 104 patients; 76 patients with PTC after thyroidectomy underwent both FNAC and thyroglobulin washout (FNAB-Tg) testing. An FNAB-Tg cut-off of 40 ng/mL, determined by receiver-operating-characteristic analysis and consistent with published data, defined Tg positivity. Diagnostic performance—sensitivity, specificity, and predictive values—was calculated and compared for FNAC, FNAB-Tg, and their combination.</p> Results <p>FNAC identified metastasis in 76 cases (73.07%), FNAB-Tg in 82 cases (78.8%), and the combined FNAC/FNAB-Tg approach in 84 cases (80.76%). The sensitivity of the combined method (95.5%) was significantly higher than that of FNAC (87.5%) or FNAB-Tg (93.2%) alone. Notably, combining FNAC with FNAB-Tg improved specificity to 100%.</p> Conclusions <p>FNAB-Tg is a reliable and more sensitive diagnostic tool than FNAC alone for detecting cervical lymph node metastases in PTC. The combination of FNAC and FNAB-Tg offers superior diagnostic performance and should be considered as a routine component of preoperative evaluation in patients with differentiated thyroid carcinoma.</p>