Thyroglobulin Measurement in Fine-Needle Aspiration Improves the Diagnosis of Cervical Lymph Node Metastases in Papillary Thyroid Carcinoma

Background: Papillary thyroid carcinoma (PTC) is frequently associated with cervical lymph node metastases. Guidelines recommend performing ultrasound-guided fine-needle aspiration cytology (FNAC) for suspicious nodes to guide management. No specific recommendations are available for the use of FNA thyroglobulin assay (FNA-Tg). This study investigated the diagnostic value of performing FNAC and FNA-Tg. Methods: Patient demographics, preoperative investigations, surgery, and lymph node pathology were collected for patients with PTC who underwent lateral neck lymphadenectomy and central compartment reexploration from January 2000 to July 2015. Sensitivities and accuracies were obtained. Patients with both diagnostic studies performed were compared using McNemar’s test of paired proportion. Patient, imaging, and lymph node characteristics were correlated with test accuracy. Results: The 480 patients in this study underwent 706 lateral neck dissections or central compartment reexploration. All the patients underwent preoperative neck ultrasound. Among these patients, FNAC alone was performed before 426 operations (60 %), FNAC with FNA-Tg before 105 operations (15 %), and surgery without biopsy for 175 patients (25 %). The sensitivity, positive predictive value, and accuracy were respectively 96, 95, 100 % for FNAC, 99, 97, and 97 % for FNA-Tg, and 95, 92, and 97 % for FNAC in combination with FNA-Tg. In the subgroup of patients who had both tests performed, the sensitivity of FNA-Tg was superior to that of FNAC (95 vs 87 %; p = 0.04). The addition of FNA-Tg to FNAC increased the detection of metastatic PTC by 13 %. Conclusions: For diagnosing cervical lymph node metastases in PTC, FNA-Tg is a valuable adjunct to FNAC. Its use should be considered to avoid missing metastatic disease in patients who may benefit from lymphadenectomy.