Variant Philadelphia translocation in an immunologically and clinically typical case of chronic myeloid leukaemia

Cytogenetic analysis of bone marrow from a chronic myeloid leukemia patient in chronic phase revealed a classical Philadelphia chromosome from a complex translocation t(2;9;22). The break points on 9 and 22 were, apparently, the same as for the standard translocation (9;22). However, whereas the terminal band of 9 (9q34) was translocated in the usual site, that is on 22q-, the tract deleted from 22 was present on band p13 of chromosome 2. The finding of this rare 22 translocation in classical CML would seem to support the hypothesis that the crucial event in the pathogenesis of CML is the translocation of band 9q34, that contains the c-abl oncogene, onto the Ph' chromosome, rather than the translocation of the tract deleted from 22 to some other chromosome site.