Non-biased and complete case registration of lymphoid leukemia and lymphoma for five years: a first representative index of Japan from an epidemiologically stable Miyagi Prefecture.

Previous worldwide epidemiological studies on lymphoid leukemia and/or lymphoma (LL/L) had considerable bias because of difficulty in covering all clinical departments of hospitals in a restricted area (population base). These studies may not have reflected the actual number of newly diagnosed cases (incidence) strictly, or the true LL/L subtype frequencies. We searched all cases of newly diagnosed LL/L in Miyagi Prefecture over a 5-year period, including those that were discovered as LL/L sorely after autopsy. We registered the actual number of 2098 cases in the prefecture and calculated an accurate incidence rate (17.8 per 100,000 persons). Additionally, we identified more realistic and detailed frequencies of LL/L subtypes including the leukemic phase of some lymphomas. As Miyagi Prefecture is an area in which the population dynamics are relatively stable and representative of Japan, the result of our epidemiological study can be used as the first representative index of LL/L for Japan.