Thyroid Carcinoma in Japan and the West: Similarities and Differences.

Geographic or ethnic differences in the incidence of thyroid carcinoma, as well as in the histologic distribution of thyroid carcinoma between Japan and Western countries, have been described but are still unclear. The recent establishment of histologic criteria for the diagnosis of thyroid carcinoma by the WHO committee has facilitated the comparison of clinicopathological data of patients with thyroid carcinoma all over the world. The aim of the present review article is to clarify the epidemiological and clinicopathological differences of thyroid carcinoma between Japan and Western countries. We found recently no significant differences in the incidence, mortality, and histologic distribution of thyroid carcinoma between Japan and Western countries; this was contrary to our expectation. This is likely attributable to westernization of the Japanese diet, standardized medical levels, and international standardization of histologic criteria of thyroid carcinoma.