Differentiated thyroid cancer (DTC) patients treated by surgery may develop recurrence in the form of metastatic lymph nodes, meaning that long-term follow-up is important. Cytological analysis of the washout from a fine needle aspiration (FNA) biopsy to determine thyroglobin (Tg) levels has been reported previously to have 100% sensitivity and 96% specificity and is recommended for follow-up of DTC patients. However, there is no standardized method in performing the needle washout, and the possibility of interferences between Tg and Tg antibodies has been suggested. A study by Borel et al., used 34 DTC patients with 53 cervical lymph nodes, 26 non-thyroidectomized patients with thyroid-unrelated cervical mass as negative controls and 13 patients with 21 thyroid nodules as positive controls, from which the levels of FNATg were measured. All 26 negative controls showed FNATg levels less than 1ng /FNA while all 21 positive controls showed FNATg levels 127 – 210 000 ng/FNA. Among the DTC patients 25 lymph nodes in 16 patients were benign and showed 1 with low FNATg levels (6ng/FNA) while the remainder were undetectable; 19 lymph nodes with a malignant cytology showed high FNATg levels, except in 2 oncocytic DTC metastasis (6.6 and 7ng/FNA), finally FNATg was also high in a lymph node with a non-informative FNA cytology which proved to be a DTC metastasis. FNA was performed using spinal needles, cells were spread onto a glass slide and 1 ml saline solution was aspirated through the needle using a triple pumping action. The washout was analysed using an IRMA to determine FNATg levels. The results show the correct detection of thyroid cells in the FNATg of the positive group and no evidence of interference of serum Tg in the negative group. The authors conclude that the method of FNATg of lymph nodes reported in this study provides a useful method of detecting lymph node metastasis in the follow-up of DTC patients and that low levels of FNATg can be an indication of DTC metastasis. Borel, A-L., Boize, R., Faure, P., Barbe, G., Boutonnat, J., Sturm, N., Seigneurin, D., Bricault, I., Caravel, J-P., Chaffanjon, P., Chabre, O. European Journal of Endocrinology, 158, 691-698. DOI: 10.1530/EJE-07-0749