Thyroglobulin measurements in washouts of fine-needle aspiration biopsy in the monitoring of patients with differentiated thyroid carcinoma

Approximately 35% patients with papillary thyroid carcinoma (PTC) and 13% with follicular thyroid carcinoma (FTC) present with metastases of cervical lymph nodes (LNs) at the time of diagnosis. In addition, 15-20% of patients treated with total thyroidectomy develop, after an interval of five years, metastases to the neck LNs on ultrasound examination. Fine-needle aspiration biopsy (FNAB) represents the gold standard technique for the detection of cervical LNs metastases. The aim of the study was to evaluate the diagnostic performance of the technique of thyroglobulin (Tg) measurement of washout FNAB (FNAB-Tg) in diagnostics of LNs metastases in different groups of patients with differentiated thyroid carcinoma (DTC). Two hundred FNAB-Tg samples from 200 patients [158 women; 42 men; mean age 51.37 ± 16.77 (53)] diagnosed with DTC were examined for the assessment of the diagnostic utility of FNAB-Tg from suspicious LNs. FNAB-Tg ranged from 1.96 to 5000 ng/mL in metastatic LNs [mean; 1510 ± 1486 ng/mL (958.5)] and from 0.04 to 635.9 ng/mL in nonmetastatic LNs [mean; 57.86 ± 319.19 ng/mL (1.96)], p < 0.001. The most accurate diagnostic performance was displayed for the concentration of 33.28 ng/mL in FNAB-Tg with AUC of 0.91 and high sensitivity and specificity (0.92 and 0.93). FNAB-Tg in conjunction with the cytopathological examination of suspicious LNs in differentiated thyroid carcinoma (DTC) patients increases the diagnostic accuracy of FNAB (sensitivity 0.99; specificity 0.99; AUC 1.00). FNAB-Tg may be particularly useful in detecting LN metastases in DTC patients, and in differential diagnosis of various LN metastasizing malignancies. The combination of FNAB and FNAB-Tg measurement has high specificity and sensitivity in the detection of LN metastases of DTC.