BCR and chronic myelogenous leukemia, BCR-ABL1 positive: <h4>Background</h4>Blast transformation of chronic myelogenous leukemia (CML) to T lymphoblastic lymphoma/acute lymphoblastic leukemia (T-LBL/ALL) is rare, and the molecular mechanism is still unclear.<h4>Case report</h4>A 28-year-old woman who developed T-ALL with coexpressing both p210 and p190 BCR-ABL transcripts five years after the initial diagnosis of CML in chronic phase.