Regional incidences of adult T-cell leukemia/lymphoma with cutaneous involvement in Japan.

Between 2008 and 2015, 462 newly-diagnosed adult T-cell leukemia/lymphoma (ATLL) patients with cutaneous involvement were found from the nationwide registry for Japanese patients with cutaneous lymphoma, of which 391 were selected for the study. They ranged in age from 28 to 93 years (median, 69 years), and included 215 men and 176 women (male : female ratio = 1.2). The 391 patients comprised 193 (50%) with smoldering type, 52 (13%) with chronic type, 44 (11%) with lymphoma type and 102 (26%) with acute type. The total number of patients in Kyushu/Okinawa was 8.8-times higher than that in Kanto, which was set as the reference value, while the estimated prevalence of human T-lymphotropic virus 1 (HTLV-1) carriers in Kyushu/Okinawa has been reported to be only 2.5-times higher than that in Kanto. In this study, the annual incidence of ATLL per 100 000 residents in Kyushu/Okinawa was 32-times higher than that in Kanto. Our results indicated the higher incidence rate of ATLL in the endemic area than those in the non-endemic areas in Japan, compared with the regional differences of HTLV-1 prevalence determined by serological HTLV-1 screening for blood donors. In addition, this analysis revealed that regional differences of mycosis fungoides/Sézary syndrome incidence rates were very small compared with those of ATLL.