Abstract:

Objective To provide a reference for the diagnosis of metastatic differentiated thyroid carcinoma（DTC）,through determining the level of thyroglobulin（Tg） in washout fluid of fine needle aspirate（FNA） for suspicious cervical lymph nodes.Methods A total of 145 FNA washout fluid samples were collected from suspicious cervical lymph nodes of patients with DTC after surgery by B ultrasound,and 16 FNA washout fluid samples of cervical reactive proliferation lymph nodes were used as control group. The FNA-Tg levels were determined by chemiluminescence immunoassay. Combined with pathological analysis,the difference of FNA-Tg levels between negative lymph nodes（27 cases）and metastasis lymph nodes（118 cases）was analyzed retrospectively. Combined with cytological analysis,the diagnosis efficiencies for different FNA-Tg cut-off values were evaluated. Results The FNA-Tg level in metastasis lymph node group [median（P₂₅-P₇₅）] was 4 163（273-13 138）ng/mL,which was higher than that in negative lymph node group [0.1（0.1-0.2）ng/mL]（P<0.01）. The diagnosis sensitivity of cytological analysis was 83.1%,and the specificity was 100%. For cytological analysis,the diagnosis sensitivities were 96.6% and 91.5%,when the cut-off values were 4.7 and 47.1 ng/L,and the specificities were 92.6% and 100%. Combined with cytological analysis,when the cut-off values were 1,5,10,50 and 100 ng/mL,the sensitivities were 97.5%,97.5%,96.6%,96.6% and 96.6%,and the specificities were 88.9%,92.6%,92.6%,100% and 100%. Conclusions FNA-Tg method is an auxiliary method for the determination of lymph node metastasis in the diagnosis of DTC. When the result of cytological analysis is positive,and FNA-Tg cut-off value is > 5 ng/mL,metastasis is from DTC. When the result of cytological analysis is negative,and FNA-Tg cut-off value is >50 ng/mL,lymph node has DTC metastasis.

Key words: Differentiated thyroid carcinoma, Lymph node metastasis, Thyroglobulin