Lymph node thyroglobulin in the diagnosis of metastases of thyroid carcinoma with the thyroid in situ: A prospective intraoperative study

Background: The use of thyroglobulin concentration in washout fluid of fine-needle aspiration (FNA-Tg) is a procedure advocated by international guidelines to diagnose metastatic LN in papillary thyroid cancer. With the increasing use of active follow-up or lobectomy alone for low-risk thyroid cancers, the determination of the diagnostic performance of FNA-Tg in the detection of metastatic PTC when the thyroid is in situ is paramount.Materials and methods: Prospective study with measurement of Tg in washout fluid obtained from intraoperative fine needle aspiration (FNA) cytology in order to avoid contamination from thyroid tissue and rigorously isolated punctured nodes. Receiver-operating characteristic (ROC) curve and area under the curve (AUC), optimal threshold to discriminate benign and malignant LN, sensitivity and specificity were provided.Results: a total of 58 lymph nodes from 32 patients were analyzed. ROC analysis defined the optimal cutoff values of FNA-Tg at 60 ng/ml for the diagnosis of malignant LNs in patients with a thyroid in situ. Sensitivity and specificity were 75% (95% confidence interval 57.89-86.75) and 87.5% (95%CI: 69-95.66), respectively.Conclusion: Our results support the hypothesis that the Tg-FNA threshold for a safe diagnosis of LN metastasis in PTC is higher in presence of a thyroid gland in situ. The use of lower thresholds could result in false positive results and lead to unnecessary surgery.(c) 2022 Elsevier Ltd, BASO -The Association for Cancer Surgery, and the European Society of Surgical Oncology. All rights reserved.

Automated summary

The use of thyroglobulin concentration in washout fluid of fine-needle aspiration (FNA-Tg) is recommended for diagnosing metastatic lymph nodes (LNs) in papillary thyroid cancer (PTC). This study aimed to determine the diagnostic performance of FNA-Tg in detecting metastatic PTC in the presence of an intact thyroid gland. The results indicate that the optimal cutoff value for FNA-Tg in diagnosing malignant LNs is 60 ng/ml, with a sensitivity of 75% and specificity of 87.5%. Therefore, using lower thresholds may result in false positive results and unnecessary surgery.