One study showed that the preoperative calcitonin level is associated with the extent of tumor and the number of lateral lymph node metastases in MTC (n = 170); thresholds of 20.1, 200.1, and 500.1 pg/mL were identified for ipsilateral LLNM, contralateral LLNM, and distant metastasis, respectively,13 while 20 and 200 pg/mL were recommended by other doctors for ipsilateral and contralateral prophylactic lymph node dissection, respectively.1, 14. This evidence concerns the gene CALCA and medullary thyroid gland carcinoma.