Detection of translocation 8;21 on interphase cells from acute myelocytic leukemia by fluorescence in situ hybridization and its clinical application

To detect a translocation (8;21)(q22;q22) in interphase cells by fluorescen ce in situ hybridization (FISH), we investigated three probe combinations: single-color hybridization with two cosmid probes (cY8 and cY3), single-col or hybridization with four cosmid probes (cY8, cY3, cY107, and cYR4), and d ual-color hybridization with two cosmid probes (cY107 and cYR4) from the AM L1 gene flanking or overlapping the breakpoint region. Over 95% of nuclei g ave sufficient signals in all three probe combinations, and the detection r ates were not statistically different among them. Among 18 patients examine d at diagnosis, 12 with t(8;21) were also monitored for the number of resid ual leukemic cells after chemotherapy or bone marrow transplantation (BMT). There were some discrepancies between mor phology and genetic (especially FISH) results at partial, or even complete remission. As leukemic cells wit h t(8;21) can maturate, morphological assessment alone is insufficient to e valuate the residual leukemic cells. Interphase FISH provided more precise information about the clinical status of patients with an 8;21 translocatio n after treatment. (C) Elsevier Science Inc., 1999. All rights reserved.