Detection of Central Compartment Lymph Node Metastasis of Thyroid Cancer: Usefulness of Intraoperative Thyroglobulin Measurement in Fine Needle Aspiration Washout with and Without Blue Dye Injection

<b>Background/Objectives</b>: The management of lymph node metastases of the central neck compartment (CNC) in differentiated thyroid carcinoma is debated. The intraoperative measurement of thyroglobulin (Tg) has gained attention in accurately detecting metastases, reducing unnecessary CNC dissections. <b>Methods</b>: A total of 37 patients underwent surgery. An intraoperative assay of thyroglobulin from fine needle aspiration (Tg-FNA) was performed on CNC lymph nodes, identified by blue dye injection in 15 patients (23 nodes, group A) and by palpation in 22 patients (35 nodes, group B). The Tg-FNA values were compared with histology to calculate the diagnostic accuracy. <b>Results</b>: In group A, the blue dye diffused widely, complicating lymph node identification: 2 were metastatic and 21 non-metastatic, with median Tg-FNA levels of 6236 ng/mL and 99.20 ng/mL, respectively. In group B, 8 were metastatic and 27 benign, with median Tg-FNA levels of 4063 ng/mL and 121 ng/mL (<i>p</i> < 0.0001), respectively. ROC analysis identified 500 ng/mL as a cutoff, achieving 100% sensitivity and 74% specificity in group B and 90% sensitivity and 70% specificity overall. Finally, among the non-metastatic lymph nodes, group A exhibited some cases of very high Tg-FNA values compared to group B, with lower accuracy for the cutoff, suggesting that colorant injection might lead to increased Tg-FNA levels. <b>Conclusions:</b> Blue dye injection showed low accuracy. Intraoperative Tg-FNA was reliable in detecting CNC metastases, although a higher cutoff is needed in this compartment compared to what has been reported for lateral lymph nodes. Lymphatic drainage and surgical manipulation might explain these findings. The careful interpretation of Tg-FNA in CNC should be adopted.