We wanted to evaluate the utility of thyroglobulin measurement in the washout of the needle (FNA-Tg) used for fine needle biopsy for detecting lymph node metastasis in patients with differentiated papillary thyroid carcinoma (DPTC).

We performed ultrasonography-guided fine-needle aspiration cytology (FNAC) and FNA-Tg for 50 ultrasonographically suspicious lymph nodes in 45 DPTC patients. Eighteen patients underwent thyroidectomy before FNA and the remaining 27 patients underwent fine-needle aspiration prior to surgery. The final diagnoses were determined based on the results of histological examination of the excised specimens (n=21) or on the follow-up examination that was done least 12 months after surgery.

Lymph node metastases were confirmed in 19 patients. FNAC detected 14 metastatic lymph nodes in 14 patients, and FNA-Tg detected 18 metastatic lymph nodes in 18 patients. While none of 3 cystic lymph nodes metastasis was detected via FNAC, they all revealed positive results via FNA-Tg. One patient with a negative result on both methods had one metastatic lymph node among 9 excised lymph nodes, and this one node had not been sampled via FNAC or FNA-Tg. The sensitivities and specificities of FNAC and FNA-Tg were 73.6% (14/19) and 100% (27/27), and 94.7% (18/19) and 96.2% (26/27), respectively.

FNA-Tg is a useful technique for the early detection of lymph node metastasis, and especially for detecting cystic lymph node metastasis in patients with DPTC.