Is Associated With a Poor Prognosis in Childhood Acute Lymphoblastic Leukemia

regardless of the proportion of normal metaphases.For cases with more than one leukemic line due to clonal evolution, only the primary line was included in the analyses, with the exception of a single case of hypodiploidy in which the secondary line containing a translocation was used. DNA content determination byflow cytometry. Leukemic marrow samples were stained with a DNA-specific dye, propidium iodide, and were analyzed by flow cytometry as previously described.’6 The DNA index (ratio of DNA content in leukemic GO/G, cells v normal diploid G0/G, cells) was determined. This measure correlates closely with chromosome number (ploidy); hence leukemic cells with a normal chromosome number have a DNA index of I .0. Blast cell phenotyping. The diagnosis of ALL was based on morphological criteria of the French-American-British (FAB) group’7 and negative myeloid-associated cytochemical findings. Cell-surface antigens were detected by a standard indirect immunofluorescence assay with monoclonal antibodies (MoAbs) to lym