Philadelphia Chromosome–like Mixed-Phenotype Acute Leukemia Demonstrating P2RY8-CRLF2 Fusion and JAK1 Mutation

Objectives: Philadelphia chromosome-like (Ph-like) genetic alterations define a subset of B lymphoblastic leukemia/lymphoma (B-ALL), which represents a separate provisional entity in the World Health Organization 2016 updated classification. However, these alterations have not been described outside the context of B-ALL. Methods: Cytogenomic array and molecular analysis identified a Ph-like signature in a mixed-phenotype acute leukemia (MPAL), B/myeloid, confirmed using conventional immunophenotypic and cytochemical analysis. Results: Flow cytometry identified a blast population demonstrating a B-cell lineage and myeloperoxidase positivity. A P2RY8-CRLF2 fusion and JAK1 mutation were detected, both of which are associated with Ph-like features. Conclusions: To our knowledge, this is the first report of Ph-like MPAL, which may represent a new diagnostic entity. We emphasize the need for refinement of diagnostic criteria for MPALs and highlight an opportunity for expansion of inclusion criteria in ongoing clinical trials studying the use of tyrosine kinase inhibitor therapy to include cases of Ph-like MPAL.