Persistence of the AML1/ETO transcript has been demonstrated by PCR in patients with t(8;21) in long-term remission, but the rearranged AML1 gene could not be detected by Southern analysis, showing that the t(8;21) clone existed as minimal residual disease (MRD).     ///    "In one patient with t(8;21), AML1/ETO could be detected serially in the peripheral blood. "    ///    "Thus, the presence of AML1/ETO in this case appeared to be due to persistence of the mutated clone as mature myeloid cells instead of MRD, implying that the t(8;21) had occurred in a preleukemic myeloid progenitor cell capable of differentiation.. "    ///    " Translocation (8;21)(q22;q22) involves fusion of the AML1 gene with the ETO gene, generating an AML1/ETO fusion transcript that can be detected by the polymerase chain reaction (PCR). "