Revisiting the guidelines issued by the Japanese Society of Thyroid Surgeons and Japan Association of Endocrine Surgeons: a gradual move towards consensus between Japanese and western practice in the management of thyroid carcinoma.

Background: In 2010, the Japanese Society of Thyroid Surgeons (JSTS) and Japanese Association of Endocrine Surgeons (JAES) established new guidelines entitled "Treatment of Thyroid Tumors." Since then, several new studies, including those that address the treatment of differentiated thyroid carcinoma (DTC) have been published, and the DTC treatment policy not only of Japanese physicians but those in Western countries has continued to evolve.

Methods: We selected six clinical questions regarding the treatment of DTC and revisited them based on newly published data from Western countries and Japan.

Results: More data have accumulated about treatment of low-risk papillary microcarcinoma. It has become clear that conservative treatment (observation) of low-risk papillary microcarcinoma in elderly patients is an acceptable alternative to immediate surgery. Total thyroidectomy versus hemithyroidectomy for low-risk papillary thyroid carcinoma (PTC) has become an important issue, and some publications after 2010 indicated that hemithyroidectomy is adequate for these low-risk patients. Unfortunately, no published manuscripts on prophylactic central node dissection offered good evidence regarding its indications or included a large number of patients. Also, it was not evident that prophylactic lateral node dissection improves cause-specific survival, although it might reduce lymph node recurrence especially in PTC patients with large tumors, distant metastases, or clinical central node metastases. Although completion total thyroidectomy was not recommended for minimally invasive follicular thyroid carcinoma in our guidelines, it may be better to perform it in elderly patients and those with a large tumor or extensive vascular invasion. Radioactive iodine (RAI) ablation after total thyroidectomy is still performed almost routinely in many Western institutions, although recent studies showed that ablation is not beneficial in low-risk patients. In Japan, because of legal restrictions, most patients did not undergo RAI ablation, and their prognoses are excellent.

Conclusions: Recently, policy for treating DTCs has changed not only in Western countries but also in Japan, resulting in a gradual move toward consensus between Western practice and ours. We will continue to present the best treatments for patients with thyroid carcinoma each time we revise our guidelines.