Is the prognosis of total thyroidectomy better than lobectomy for patients with papillary thyroid cancer? There is insufficient evidence that thyroidectomy improves survival in patients with papillary thyroid cancer. Total thyroidectomy prevents tumor recurrence in the residual thyroid, but does not reduce the chance of lymph node and distant metastases. Therefore, the guideline development committee recommended total thyroidectomy for high-risk patients. High-risk patients include tumors greater than 5 cm in length, extra-glandular infiltration, invasion of esophageal or tracheal mucosa, regional lymph node metastases (greater than 3), and distant metastases. Total thyroidectomy is recommended for high-risk patients. Low-risk patients include tumor length diameter less than or equal to 2 cm, no regional lymph node metastasis (T1N0M0 in TNM stage), etc. Lobectomy is also acceptable for low-risk patients. For the rest of the patients, the scope of thyroidectomy was in the “gray area” and the committee agreed that total thyroidectomy was recommended for patients with tumor diameter greater than 4 cm and regional lymph node metastasis (N1). In Japan, the scope of thyroidectomy is traditionally different from that of some other countries. According to ATA guidelines, total or near-total thyroidectomy is routinely recommended for differentiated thyroid cancer, except for patients with low-risk microscopic cancer. the BTA guidelines recommend total thyroidectomy for most patients with thyroid cancer, especially those with thyroid masses larger than 1 cm, multiple foci, extralobar invasion, history of family disease, history of neck radiation, and clinical lymph node metastases. the AACE/AAES guidelines Total thyroidectomy is recommended, especially for patients with tumors in both lobes, tumors in the center of both lobes, extralobar invasion, and local or distant metastases who are classified as high risk by various classification systems (e.g., MACIS, AMES, EORTIC, etc.). In the NCCN guidelines, cases meeting all of the following clinicopathologic features can undergo lobectomy on one side of the gland: 15 to 45 years of age, no history of radiation exposure, no distant metastases, no lymph node metastases, no extralobar invasion, tumor diameter less than 4 cm, and no signs of aggressive changes. Even for these patients, the guidelines state that “total thyroidectomy is the more common strategy”. In contrast, limited thyroidectomy such as subtotal thyroidectomy or lobectomy with isthmus is widely accepted in Japan. Further precise analysis would require the collection of more than 1000 cases over decades of follow-up. However, it is difficult to maintain a consistent level of diagnosis, uniform surgical design, and perfect postoperative follow-up over a long period of time, even at a single institution. Not to mention that total thyroidectomy is often combined with radioactive iodine therapy in the West, which means that these studies do not really achieve comparable efficacy between total thyroidectomy and limited thyroidectomy. The few studies reported so far showed no positive findings based on prognostic comparisons between different surgical scopes. A report from Japan showed that patients with solitary papillary thyroid cancer in stage T1N0M0 who underwent hemithyroidectomy had only a 1% chance of postoperative residual thyroid recurrence. In conclusion, there is no high-level evidence that total thyroidectomy improves patient prognosis, especially in terms of postoperative survival. Considering the above data base and the social reality in Japan, the committee reached a consensus after discussion that total thyroidectomy is required for high-risk patients and that total thyroidectomy is not necessary for patients with T1N0M0 and no lesions in the contralateral gland lobe.