MLL Rearrangment and EVI1 Deletion in BCR/ABL1 Positive Chronic Myeloid Leukemia

We present unusual cytogenetic findings in a 65-year-old female with blast phase (BC) of Philadelphia chromosome positive chronic myeloid leukemia (CML). Chromosome analysis revealed two related abnormal clones, one characterized by a t(9;22)(q34;q11.2), and the other showing a t(11;19)(q23;p13.1) in addition to the t(9;22)(q34;q11). Fluorescence in situ hybridization (FISH) testing confirmed that the t(11;19) involved the MLL gene on 11q23. High-density whole-genome SNP array analysis of leukemia cells showed a number of submicroscopic copy number abnormalities, including a deletion of the MECOM (MDS1 and EVI1 complex locus protein EVI1) gene at 3q26. Clinical course was aggressive, and the patient failed to respond to both imatinib and dasatinib despite the absence of resistance-associated mutations in the BCR/ABL1 gene. To our knowledge, the combination of a t(9;22) with t(11;19)(q23;p13.1) has only been reported in one case, while a deletion of the EVI1 gene has never been reported in CML.