Donor‐Derived CD19‐CAR‐T Therapy in Combination With TKI Cures Uncommon Ph‐Like Mixed‐Phenotype Acute Leukemia With Lineage Switch to Ph+ Acute Lymphoblastic Leukemia: A Case Report

Abstract

Mixed phenotype acute leukemia (MPAL) is a rare hematologic malignancy characterized by the presence of a single population of cells expressing antigens of two or more lineages or by two or more populations of blast cells with different lineage features. Lineage switch (LS) is a rare and specific type of relapse, which can manifest as the conversion of acute lymphoblastic leukemia (ALL) to acute myeloid leukemia (AML) or vice versa. Previous reports indicate that patients with lineage-switched leukemia often harbor KMT2A rearrangements (also known as MLL ; rearrangements referred to as KMT2Ar ) or BCR::ABL1 fusion gene (also known as Philadelphia chromosome positive; Ph + ). In recent years, with the increased use of CD19-CAR-T therapy, some LS cases have been reported [ 1 ]. It was suggested that the non-KMT2Ar lineage-switched leukemia is associated with a potential impact of BCOR/BCORL1 truncating mutation on cellular plasticity [ 2 ]. Here, we report a case of CRLF2r -MPAL without