Thyroglobulin determination in fine needle aspiration biopsy washout of suspicious lymph nodes in thyroid carcinoma follow up

Background: Differentiated thyroid carcinomas (DTCs) account for about 1% of all human malignancies. Cervical lymph nodes metastases and recurrences in the thyroid bed frequently occur. Furthermore, about 10-15% of patients develop distant metastases. Therefore, patients must undergo life-long follow-up. Objective: The aim of this study was to evaluate the usefulness of Thyroglobulin measurement in FNAB washout (FNAB-Tg) in the detection of local metastasis in patients affected by or evaluated for thyroid cancer. Materials and Methods: In a 3-year period, a total of 83 consecutive patients coming to our attention at the Ear-Nose-Throat (ENT) Outpatients Service of the National Cancer Research Center "Istituto Tumori Giovanni Paolo II" of Bari, Italy, because of the finding of one or more cervical lymph node(s), were enrolled in the study. After collection of the cytological specimen, the needle used for performing FNAB was then washed in 1 ml of normal saline. 89 FNAB washouts were collected from the same number of lymph nodes and subsequently investigated for Thyroglobulin levels using a sequential chemiluminescent-immunometric assay. Results: Comparing the cytological or, when performed, histological diagnoses with the results of FNAB-Tg, we found that in 24 cases of lymph node metastases from PTC (19 lymph nodes from patients at the first diagnoses and 5 lymph nodes from PTC patients in follow up) the mean level of Thyroglobulin was 1840.11 ng/ml; range: <0,2 to 11440 ng/ml. In the group of PTC patients (27 lymph nodes) with lymph nodes negative for metastatic involvement at cytology (i.e. no lymph node recurrence at follow-up), as well as in the cases of subjects without PTC and submitted to FNAB because of the appearance of lymph node(s) classified as reactive at cytology (37 lymph nodes), FNAB-Tg was lower than or equal to 0.2 ng/ml. As expected, the Thyroglobulin level was not detectable (< 0.2 ng/ml) also in a lymph node FNAB from a case of anaplastic thyroid carcinoma. Conclusion: In our study, FNAB-Tg was not detectable in all node negative patients showing, when considering together all the lymph node metastases, a 96% sensitivity and 100% specificity.