Acute Lymphoblastic Leukemia With Near-haploid Karyotype and Philadelphia Chromosome

In precursor B-cell lineage acute lymphoblastic leukemia (BCP-ALL), leukemic cells harbor genetic abnormalities that play an important role in the diagnosis, prognosis, and treatment. A subgroup of BCP-ALL is characterized by the presence of a Philadelphia (Ph) chromosome and a chimeric BCR::ABL1 gene, whereas in another subgroup, leukemic cells exhibit near-haploidy with chromosome number 24-30. This study presents the third documented case of BCP-ALL in which a near haploid clone concurrently displayed a Ph chromosome/BCR::ABL1.

Bone marrow cells obtained at diagnosis from a 25-year-old man with BCP-ALL were genetically investigated using G-banding, fluorescence in situ hybridization, and array comparative genomic hybridization. Leukemic cells had an abnormal karyotype 28,X,-Y,+6,+10,+18,+21,+ der(22) t(9;22)(q34;q11)[13]/28,idem, del(10)(q24),der(12) t(1;12) (q21;p13)[2]/46,XY[3], retained heterozygosity of the disomic chromosomes 6, 10, 18, and 21, had breakpoints in introns 1 of ABL1 and BCR, and carried a BCR::ABL1 chimera encoding the 190 kDa BCR::ABL1 protein.

The coexistence of the BCR::ABL1 chimera and near-haploidy in the same cytogenetic clone suggested a possible synergistic role in leukemogenesis, with the former activating signaling pathways and the latter disrupting gene dosage balance.