The Role of Intraoperative Thyroglobuline Level of Lymph Node in the Management of Papillary Thyroid Cancer (Determination of a Cutoff Point)

BACKGROUND: Some studies have shown that a preoperative high concentration of thyroglobulin (Tg) in wash out of fine-needle aspiration cytology of cervical lymph nodes mandate therapeutic lymph node dissection. However, there is disagreement about the minimum concentration of Tg which could have diagnostic value. Hence, according to our literature review, this study is the first one which designed to do intraoperatively. Therefore, this study was conducted and aimed to determine the clinical diagnostic value of Tg lymph nodes in the diagnosis of metastatic thyroid cancer. METHODS: In a cross-sectional study, 65 patients with papillary thyroid carcinoma (PTC) who were thyroidectomy candidates were chosen and during surgery, before the removal of lymph nodes in the neck, fine-needle sampling was performed and the level of Tg in the samples, nature of the sample sent for biopsy and Tg levels in affected and unaffected lymph nodes were determined. RESULTS: The mean levels of washout Tg in malignant and nonmalignant lymph nodes were 622.1 ± 66.2 and 1.38 ± 0.43 ng/ml, respectively, and the difference between the two groups was significant (P < 0.001). The Tg cut-off point for the detection of lymph node metastases was 0.7 ng/dl, and according to it, Tg washout sensitivity was 93.8%, specificity of 92.4%, false positives 7.76%, false negatives 6.3%, positive predictive value was 92.3%, and negative predictive value was 93.8% and accuracy was 93.1%. CONCLUSION: Based on the results, Tg level of cervical lymph nodes in patients with PTC is a suitable criterion for the diagnosis of lymph node which can be determined through fine-needle biopsy. Therefore, it is suggested that in patients with suspicion of lymph nodes involvement during surgery, fine-needle biopsy and determination of the Tg level performed.