[Comparison of the incidence and trends of hematologic malignancies between Japan and the United States].

The incidence of a malignant disease reflects both genetics and the cumulative environmental exposures of a population. Therefore, evaluation of the incidence and trends of a disease in different populations may provide insights into its etiology and pathogenesis. To evaluate the incidence of hematologic malignancies according to specific subtypes, we used population-based registry data in Japan and the United States from 1993 to 2008. The age-adjusted incidence of hematologic malignancies in Japan was approximately one-half that in the United States but has been increasing significantly, whereas no significant change was seen in the United States (annual percent change: Japan, +2.4%; USA, +0.1%). Hodgkin lymphoma (HL) and non-Hodgkin lymphoma (NHL) showed the largest incidence differences, with those of chronic lymphocytic leukemia, HL-nodular sclerosis, mycosis fungoides, and cutaneous T-cell lymphoma being the most remarkable. Differences in the incidence and trends for specific subtypes also showed a marked contrast across subtypes which, in turn, may provide novel and significant future insights into disease etiology.