Amplification of the BCR::ABL1 Fusion Gene: A Rare Phenomenon in B-cell Acute Lymphoblastic Leukemia.

Abstract

clustered manner (Figure 1B) in 70% of the interphase nuclei, consistent with the amplification of the BCR::ABL1 fusion gene. The patient died within a month of the diagnosis. Additional Philadelphia (Ph) chromosomes are frequently seen in B-ALL and in cases of disease progression in chronic myeloid leukemia (CML). However, multiple extra copies of the BCR::ABL1 fusion gene are rare genetic occurrences in CML signifying disease progression and imatinib resistance. This results from a second Ph chromosome, double minutes, isoderivative chromosome 22, and isodicentric Ph chromosome [1,2]. Although extra copies of the BCR::ABL1 fusion gene were reported previously in T-ALL, they have never been documented in B-ALL [3]. This signal pattern highlights the need for FISH or other conventional cytogenetic approaches over reverse-transcriptase polymerase chain reaction studies to confirm disease progression.