Endocrine Abstracts

Backgraund: The high incidence of cervical lymph nodes (LNs) metastasis in differentiated thyroid carcinoma (DTC) and lack of effective diagnostic tools determines the need for elaboration more specific tests.

Aims: The aim of our study was to evaluate the accuracy and cut-off point of the thyroglobulin (Tg) in the washout fluid of fine-needle aspiration biopsy (FNA-Tg) in the diagnosis of DTC LNs metastasis.

Materials and methods: A retrospective studyinvolved 245 patients with recurrent DTC and suspicious cervical LNs. All patients were evaluated FNA-Tg, serum Tg levels (sTG), Tg antibodies (TgAb) and thyroid stimulating hormone (TSH). Surgical treatment was performed in 125 patients with malignant changes according to the cytology, high FNA-Tg values, sTg. Patients were divided into 2 groups with reactive (n = 23) and metastatic (n = 102) changes in LNs according to the histological examination. FNA for both cytology and FNA-Tg was performed with a 22-G needle. FNA-Tg was aspirated through the needle with a syringe from a test tube with 0.5 ml of normal saline. TSH levels were measured by electrochemiluminescence immunoassay (Architect), reference range 0.25–3.5 mIU/l. FNA-TG, sTg (3.5–77.0 ng/ml), TgAb (0–115 IU/ml) was performed on the automated system Cobas 601 (Roche, France). Clinical and laboratory data were compared using Mann Whitney U test, results are presented as median (25 and 75 quartiles), P < 0.05. Diagnostic significance and the best cut-off value for FNA-Tg for the malignancy was performed using receiver operating characteristic curve analysis (ROC). All analyses were performed using the SPSSv23 Statistic (USA) and MedCalc v. 18.2.1 (Belgium) software.

Results: All patients were comparable by clinical (sex, age) and laboratory (TSH, sTG, Tg Ab) parameters. The median FNA-Tg in metastatic group was 537.0 [0.1; 1000] ng/ml while in benign group it was 17.9 [0.5; 158.0] ng/ml, P = 0.003. The sensitivity of isolated FNA was 85%, specificity 57%, AUC = 0.618, 95% CI 0.516–0.713. The sensitivity and specificity of FNA-Tg was 73% and 100%, respectively, AUC = 0.865, 95% CI 0.78–0.92. The optimal cut-off point for the malignancy was >9.2 ng/ml (sensitivity 75%, specificity 100%), Youden Index 0.73.

Conclusions: Our results showed that additional measurement of the Tg in the washout fluid enhances the sensitivity of isolated FNA in evaluation of DTC lymph nodes metastasis. In our population the cut-off value > 9.2 ng/ml can be proposed as a diagnostic threshold for the definition of malignancy.