Cytogenetic biclonality in malignant hematologic disorders

Generally, malignant hematologic disorders have been believed to be of monoclonal origin. However, cytogenetically unrelated clones have been reported in some disorders including one case of acute leukemia (AL), one of acute lymphoblastic leukemia (ALL), one of acute myeloblastic leukemia (AMMoL), and five of myelodysplastic syndromes (MDS). The most frequent chromosome abnormality was trisomy 8 (75%), followed by trisomy 21 (37.5%, including tetrasomy 21) and trisomy 11 (25%). Two patients showed both trisomy 8 and 11, one also had trisomy 21 (triclonal). One patient showed two cytogenetically distinctive clones in which one was 47,XY,+8, related to myeloid cells, and the other had a del(6q) and del(9p), suggesting lymphoid cells. One patient we report and 5 from the literature had two unrelated clones with trisomy 8 and deletion of the long arm of chromosome 5 (5q-); all had MDS. Review of our records showed that 11 patients with both trisomy 8 and 5q- in the same abnormal karyotype (not biclonal) had AL, i.e., 10 of acute nonlymphocytic leukemia (ANNL) and one of chronic myelogenous leukemia (CML) in blastic crisis. These findings suggest that cytogenetically unrelated clones may indicate hematopoietic biclonality.