Coexistence of p210BCR-ABL and CBFβ-MYH11 fusion genes in myeloid leukemia: A report of 4 cases

Chronic Myelogenous Leukemia with Double Philadelphia Chromosome and Coexpression of p210 and p190 Fusion Transcripts

The Philadelphia (Ph+) chromosome, t(9;22)(q34;q11.2), originates from a chimeric gene called BCR-ABL and is present in more than 90% of CML patients. Most patients with CML express the protein p210 BCR-ABL and, with a frequency lower than 5%, express rare isoforms, the main one being p190. In the transition from the chronic phase to the blast phase (BP), additional chromosomal abnormalities, such as the presence of the double Ph+ chromosome, are revealed. Of the 1132 patients analyzed via molecular biology in this study, two patients (0.17%) showed the co-expression of the p210 and p190 isoforms for the BCR-ABL transcript, with the concomitant presence of a double Ph+ chromosome, which was observed via conventional cytogenetics and confirmed by fluorescent in situ hybridization. The BCR-ABL/ABL% p210 and p190 ratio increased in these two patients from diagnosis to progression to blast crisis. To our knowledge, this is the first report in the literature of patients who co-expressed the two main BCR-ABL transcript isoforms and concomitantly presented Ph+ chromosome duplication. The evolution from the chronic phase to BP often occurs within 5 to 7 years, and, in this study, the evolution to BP was earlier, since disease-free survival was on average 4.5 months and overall survival was on average 9.5 months. The presence of the p190 transcript and the double Ph+ chromosome in CML may be related to the vertiginous progression of the disease.

Myeloid Blast Crisis of Chronic Myeloid Leukemia Followed by Lineage Switch to B-Lymphoblastic Leukemia: A Case Report

Lineage switch is very rare in blastic crisis of chronic myeloid leukemia (CML-BC). Here, we report a case of CML-BC in which the blast lineage switched from myeloid to B-lymphoid. A 35-year-old male was initially admitted to our hospital because of abdominal distention for over a year and dizziness for one week. Prior to presentation at our hospital, he visited a local hospital because of abdominal distention where his white blood cell count and bone marrow (BM) smear indicated CML. Results from peripheral blood (PB) counts, bone marrow analysis, immunophenotyping by flow cytometry, and the detection of the Philadelphia chromosome were consistent with a diagnosis of myeloid blast crisis from CML. The patient received chemotherapy with imatinib for induction, which diminished the number of blasts. However, after three months, the blasts were increased in the PB and BM. The BM study and immunophenotyping by flow cytometry revealed B-lymphoblastic leukemia. In accordance with his first admission, a chromosome study revealed a karyotype of 46, XY, t(9; 22)(q34; q11) in all 20 cells analyzed, and B-lymphoblastic transformation from CML was diagnosed. Despite three months of treatment with DVCP (daunorubicin, vincristine, cyclophosphamide and prednisone) chemotherapy in combination with dasatinib, the patient did not achieve complete remission. The patient decided to stop treatment and was discharged from the hospital for financial reasons. This case implicates the Philadelphia chromosome with p210 BCR-ABL1 fusion proteins as a key molecule in CML-BC. Further research is needed to assess the frequency, treatment, and prognosis of CML-BC patients with lineage switch.

The incidence, genetic characteristics, and prognosis of leukemia with concurrent pathogenic fusion genes: a series of 25 cases from a large cohort of leukemia patients

Recurrent fusion genes (FGs) with clinical significances in leukemias are mainly mutually exclusive, and the coexistence of different FGs has been rarely reported. In this study, we retrospectively analyzed the incidence, genetic characteristics, and prognosis of leukemias with concurrent pathogenic FGs, which commonly reported in hematological malignancies in 8226 leukemia patients. A total of 25 patients with coexistence of double FGs were identified, accounting for 0.30% of all cases enrolled. More than half of the cases (14/25, 56%) were diagnosed as chronic myeloid leukemia in accelerated or blast phase, another six and five cases were acute myeloid leukemia and acute lymphocytic leukemia, respectively. Most cases (20/25, 80%) carried constitutively activated tyrosine kinases FGs (BCR-ABL1 or ETV6-PDGFRB) and transcription factors associated FGs simultaneously. Of the 11 patients with contemporaneous karyotype, 5 (45%) showed visible chromosomal abnormalities corresponding to both FGs. The concurrency of FGs was often associated with disease progressions. The prognosis was pessimistic for patients with concurrent FGs, even with the combination of targeted therapy and chemotherapy. Performing allogeneic hematopoietic stem cell transplantation as soon as possible after complete remission can ameliorate the dismal prognosis.