Leukemia, t(8;21): Leukemia with a translocation (an exchange of material) between chromosomes 8 and 21. Seen characteristically in acute myeloid leukemia (AML) -- acute nonlymphocytic leukemia (ANLL), usually the M2 type. The breakpoints permitting the translocation to occur are in chromosome bands 8q22 and 21q22 in the ETO and AML1 genes, respectively. The translocation creates an AML1-ETO fusion gene which, in turn, leads to the production of a novel AML1-ETO protein. This unusual protein acts by repressing a tumor suppressor known as p14ARF.