A new complex translocation in chronic myelogenous leukemia with monoblastic crisis

Monocytic crisis of chronic myeloid leukemia in the era of tyrosine kinase inhibitor

A 47-year-old man was diagnosed with Philadelphia chromosome-positive chronic myeloid leukemia (CML) in October 2005. He could not receive treatment with imatinib mesylate due to his economic circumstances. He was consequently treated with hydroxyurea with partial hematological remission until June 2008. Although imatinib mesylate was started thereafter, the adherence to this treatment was poor because of his occupational circumstances. In September 2009, imatinib mesylate was switched to nilotinib, with a subsequent phase of acceleration of the disease, presumably due to his poor adherence to the treatment. Dasatinib was started in September 2010, with transient hematological response and final blastic crisis of the disease in January 2011, regardless of improved adherence. Blast cells showed immature monocytic morphology and were positive for α-naphtylbutyrate esterase staining. They also expressed surface CD14 and CD64 antigens. A diagnosis of rare monocytic crisis of CML was made. He was treated with low-dose nilotinib following cytoreduction with MEC (mitoxantrone, etoposide, and cytarabine) chemotherapy. Severe leucopenia without circulating leukemic cells continued for about 2 months with sustained hepatosplenomegaly, and he died of pneumonia in March 2012. Necropsy showed severe bone marrow hypoplasia with focal infiltration of mature leukemic cells and similar infiltration in the liver.

Novel variant Ph translocation t(9;22;11)(q34;q11.2;p15)inv(9)(p13q34) in chronic myeloid leukemia involving a one-step mechanism

Chronic myeloid leukemia (CML) is a clonal malignant disorder of a pluripotent hematopoietic stem cell characterized by the presence of a Philadelphia (Ph) chromosome. Less than 10% of patients present variant Ph chromosomes involving 1 or more additional chromosomes, other than chromosomes 9 and 22, with uncertain prognosis. There are mainly 1- or 2-step mechanisms proposed to explain the genesis of variant Ph chromosomes depending on whether the involved chromosomes are simultaneously broken and rejoined or if a standard t(9;22) occurs first. By combined standard cytogenetic and FISH analysis we detected a novel variant Ph translocation among chromosomes 9, 11 and 22 in a patient with CML without progression to an accelerated phase of the disease after 7 years, with the derivative chromosome 9 also having an acquired pericentric inversion. This novel case illustrates the use of FISH in metaphase to confirm a new rearrangement not previously described in variant Ph formation and that the present karyotype could have originated by a 1-step mechanism with 4 simultaneous breakages without deletion of ABL1.

Genomic diversity of Philadelphia-positive chronic myelogenous leukemia

The incidence of breakpoints in CML patients with variant translocations was investigated. There was no relationship between the length of various chromosomes with breakpoint frequency. However, a significantly higher (p less than 0.05) incidence of breaks were seen on the long arms as compared to the short arms due mainly to the involvement of 9q and 22q in these translocations. Chromosome 17 showed a significantly (p less than 0.005) higher involvement in these translocations, however only when 9q34-qter was not cytogenetically involved. A total of 683 breaks were found in 225 cases. 362 of these were located at c-abl and c-sis, while 110 were at other oncogenetic sites. The prognostic and hematologic features of patients with variant translocations are not significantly different from those of CML cases with the typical 9q;22q translocation. Some of these complex translocation, where the breakpoints are correlated with oncogenetic sites, are further discussed in molecular terms.