Acute Lymphoblastic Leukemia Switch Lineage upon Relapse to Acute Bilineage Leukemia: A Case Report

Although acute leukemia commonly relapses in adults, the conversion of leukemic cell lineage (lymphoid or myeloid) upon relapse has rarely taken place. “lineage switch” is a term widely used to define the leukemic lineage transformation as assessed by morphology, cytochemistry, and immunophenotyping from diagnosis to relapse. in most lineage switch cases, b-cell lymphoblastic leukemia/ lymphoma relapses as acute myeloid leukemia or vice versa. here, we report an exceedingly rare case of t-cell acute lymphoblastic leukemia relapsing as mixed phenotype acute leukemia.