When preoperative and postoperative variables related to detectable sTg were combined to be analysed, the NPVs of ablative Tg < 2.9 ng/mL were 97.7% in the patients without thyroid capsular invasion, 98.5% in the patients without lymph node metastasis, and 97.5% in the patients with preoperative Tg < 19.4 ng/mL. The gene discussed is TG; the disease is metastatic malignant neoplasm in the lymph nodes.