Molecular analysis of Philadelphia-positive childhood chronic myeloid leukemia

The breakpoints in chromosome 22 were determined in five children with Philadelphia-positive chronic myeloid leukemia. All had rearrangements within the major breakpoint cluster region (M-bcr). Four patients had breakpoints in the 5' region of M-bcr (zones 1-3), whereas one had a rearrangement in the 3' region (zone 4). The patient with the 3' rearrangement was the only one to develop a lymphoid blast crisis; he also had a substantially longer survival (102 months) than the others (11-54 months).