Philadelphia Chromosome-like Acute Lymphoblastic Leukemia: Progress in a New Cancer Subtype

Philadelphia chromosome-like (Ph-like) acute lymphoblastic leukemia (ALL) is a newly described, high-risk subtype of B-cell ALL. It is characterized by a gene expression profile similar to that of Ph-positive ALL; however, the BCR-ABL1 fusion is not present. The World Health Organization classification of myeloid neoplasms and acute leukemia recently was updated to include the Ph-like or BCR-ABL1-like ALL subtype of B-cell ALL as a provisional entity. Unlike Ph-positive ALL, which is characterized by the pathognomonic BCR-ABL1 fusion, Ph-like ALL is characterized by a multitude of different genetic rearrangements and mutations. In this review, we outline the age-related and geographic incidence of Ph-like ALL, the association with worse clinical outcomes, and early evidence for the use of ruxolitinib (a Janus kinase 2 inhibitor) and dasatinib (a tyrosine kinase inhibitor targeting ABL1).