Involvement of chromosome 9 in variant Ph1 translocation

Cytogenetic analysis of a patient with chronic myelocytic leukemia revealed a translocation (21; 22) (q 22; q 11) without a detectable involvement of chromosome 9. By in-situ hybridization studies, however, we demonstrate a reciprocal translocation of sequences from chromosome 9 (c-abl) to Ph1 and chromosome 22 (bcr) to 9, respectively. These observations suggest a consistent participation of chromosome 9 in the Ph1 translocation, regardless of the cytogenetic subtype.