Laboratory testing in BCR-ABL1-like (Philadelphia-like) B-lymphoblastic leukemia/lymphoma.

BCR-ABL1-like B-lymphoblastic leukemia/lymphoma (BCR-ABL1-like B-ALL), also known as Philadelphia-like (Ph-like) ALL, is a neoplasm of B-lineage lymphoblasts characterized by a pattern of gene expression similar to that of B-ALL with the BCR-ABL1 translocation but lacking the BCR-ABL1 fusion protein. The diagnosis of BCR-ABL1-like B-ALL is associated with a high rate of relapse and poor clinical outcomes. In recognition of the difficulty in screening these leukemias for diagnostic workup, the 2016 update/revision to the World Health Organization (WHO) 2008 edition included BCR-ABL1-like B-ALL as a provisional entity. This review addresses the various clinical considerations and methodologies currently used in the pathologic diagnosis, subclassification, and molecular characterization of cases of BCR-ABL1-like B-ALL, with particular attention paid to emerging methods useful in identification of molecular lesions potentially amenable to targeted therapy.