[Epidemiology of lymphoid and hematopoietic malignancies in Japan].

In general, the incidence and mortality rates for lymphoid and hematopoietic malignancies in Oriental countries, including Japan, are lower than in Western Europe and the U.S. However, those of lymphoid malignancies (ML) are clearly increasing in Japan, especially in the older generations. The main cause of the recent increment might be explained by compensation for risk reduction of infectious diseases in the old generations, so that their life span is extended rather than increment in exposure to specific risk factors. With regard to change in diagnostic criteria for ML, the geographical distribution of ML death rates by subtype shows variation over the last 20 years. In Japan, ML is more prevalent in southwestern districts, attributed to ATL caused by HTLV-I, and this high incidence of ATL should disappear with the HTLV-I eradication in the future. On the other hand, further diagnostic techniques might be developed and it is conceivable that a unique geographical distribution of new subtypes of lymphoid and hematopoietic malignancies may thereby be generated.