Ph-like (BCR::ABL1-like) acute lymphoblastic leukaemia

What is measured: a gene expression signature resembling BCR::ABL1-positive ALL, and then the lesion driving it. How: the signature by low-density array, RNA sequencing or a targeted classifier; the driver by flow cytometry for CRLF2 overexpression and FISH for CRLF2 rearrangement (IGH::CRLF2 or P2RY8::CRLF2, about half of cases, usually with JAK2 or JAK1 mutations), FISH or RNA sequencing for ABL-class fusions (ABL1, ABL2, PDGFRB, CSF1R), JAK2 and EPOR rearrangements, and sequencing for JAK1, JAK2, IL7R and SH2B3 mutations; IKZF1 deletion is common. It accounts for 10 to 15 percent of childhood, 25 to 30 percent of adolescent and young adult and about 20 percent of adult B-ALL, more often in people of Hispanic ancestry, with high residual disease after induction and poor survival on chemotherapy alone. What a positive result changes: ABL-class fusions get dasatinib or imatinib added, as for Ph-positive disease; JAK-STAT lesions are treated with ruxolitinib in trials (COG AALL1521); everyone is treated on high-risk arms with residual disease measured closely, and blinatumomab, inotuzumab or CAR-T are used for persistent disease with transplant considered in first remission. Where it matters: the Ph-like ALL page, adult ALL and high-risk childhood ALL.