Geographic heterogeneity of cellular characteristics of acute myeloid leukemia: a comparative study of Australian and Japanese adult cases

We assessed a large number of adults (368 from Australia and 494 from Japan ) with de novo acute myeloid leukemia (AML) to define the biological differ ences between the two populations. In this study, AML was classified using the French-American-British (FAB) criteria into seven groups (M1-M7). U2 wa s more common in Japan than in Australia, whereas M4 occurred more frequent ly in Australia than in Japan. Other FAB subtypes were evenly distributed. Cytogenetically, Japanese M2 displayed a higher frequency of t(8;21) than A ustralian (33.1% vs 15.3%, P < 0.05), The t(15;17), inv/del(16), 11q23 aber rations and 5/7/8 abnormalities were seen at similar frequencies. Immunophe notypically, Japanese M4/M5 more frequently displayed CD13 and CD14 than Au stralian, whereas the stem cell markers, CD34 and HLA-DR were observed at a relatively higher rate in Australian M3 than in Japanese M3, The B cell an tigen, CD19 was more frequently seen in Japanese M2 than in Australian M2, but found more often in Australian M5 than in Japanese M5, In both populati ons, a close relationship was observed between the expression of CD19 and t (8;21). These findings suggest different biological characteristics of AML between the two populations, the main differences being generated by a high er frequency of t(8;21) chromosomal abnormality in Japanese AML.