Usefulness of Thyroglobulin Measurement in Fine-needle Aspirates of Lymph Nodes for the Diagnosis of Lymph Node Metastasis of Papillary Thyroid Cancer

ABSTRACT

BACKGROUND: Previous studies have shown that thyroglobulin (Tg) measurement in fine-needle aspirates (FNA) of lymph nodes can assist in evaluating cervical lymph node metastasis. In this study, we evaluated the diagnostic performances of FNA-Tg, serum-Tg, and FNA-Tg/serum-Tg in detecting lymph node metastasis. METHODS: We retrospectively analyzed the diagnostic performances of FNA-Tg and serum-Tg in 641 cases (518 patients) with papillary thyroid cancer that underwent ultrasonography-guided fine-needle aspiration of cervical lymph nodes between March 2009 and February 2010. RESULTS: The number of lymph nodes and median FNA-Tg level of the positive lymph node cytology group were 99 and 1,300 ng/mL (range, 0.2-5,000), respectively, whereas corresponding values in the negative cytology group were 359 and 4.7 ng/mL (range, 0.1-1,173). The AUCs of FNA-Tg, serum-Tg, and FNA-Tg/serum-Tg ratio were 0.93 (95% CI, 0.90-0.97), 0.64 (95% CI, 0.57-0.70), and 0.83 (95% CI, 0.78-0.88), respectively. The sensitivity and specificity of FNA-Tg were 90.9% and 98.3%, respectively, and the percentage agreement with the cytology results was 96.7%. CONCLUSIONS: The agreement of FNA-Tg with the cytology results was good at the cutoff value of 35.9 ng/mL. The measurement of FNA-Tg in cases with uninterpretable cytology results can be useful in evaluating lymph node metastasis of papillary thyroid cancer.