Exploring the application of FNA-Tg for the diagnosis of cervical lymph node metastasis in PTC.

BACKGROUND

Currently, fine-needle aspiration washout thyroglobulin (FNA-Tg) are mainly utilized to assist in the detection of lateral lymph node metastasis (LLNM) in papillary thyroid carcinoma (PTC). However, there is currently no clear definition of the method, procedure, and diagnostic value of FNA-Tg testing.

METHODS

Prospectively collected data from 215 PTC patients who underwent lateral neck LNs dissection in the 900th hospital from 2022 to 2024. A total of 249 suspicious lymph nodes were included and were categorized into a metastasis group (n = 176) and a non-metastasis group (n = 73) based on postoperative pathological findings.

RESULTS

Overall analysis revealed that FNA-Tg demonstrated superior diagnostic efficacy for LLNM in PTC compared to FNAC (area under the curve [AUC] = 0.950 versus 0.766). The optimal diagnostic thresholds were determined to be 16.45 μg/L for the primary LLNM group and 0.15 μg/L for the recurrent LLNM. Subgroup analysis indicated that a statistically significant difference in the diagnostic performance of FNA-Tg and FNAC for PTC LLNM was observed only when the LN short diameter was ≤0.8 cm (p < 0.001). Further more, when thyroglobulin antibody (TgAb) results were negative, the combination of the optimal threshold for FNA-Tg and the FNA-Tg/serum thyroglobulin (sTg) ratio was determined to be the most effective diagnostic criterion (criterion ③; AUC = 0.943).

CONCLUSION

FNA-Tg has a higher diagnostic value for PTC LLNM, especially in small LNs.