Acute myelomonocytic leukemia with marrow eosinophilia showing 5q- and 16q22 mosaicism.

We report an 82-year-old Japanese female with acute myelomonocytic leukemia with dysplastic marrow eosinophilia (FAB M4Eo) exhibiting a partial deletion of the long arm of chromosome 5, del(5)(q13q31) and a derivative chromosome 16 with a breakpoint at band 16q22, in addition to 5q-. The patient had a history of a preleukemic phase for several months with marked dysplasia in trilineage marrow cells, in addition to leukemic features compatible with M4Eo. These findings strongly suggested that the leukemic cells in this case were derived from a preleukemic clone with a del(5q).