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Early Lineage Switch from T-Acute Lymphoblastic Leukaemia to Common B-All

Case report

Abstrak

Abstract

Leukaemic  stem  cells  have  heterogenous  differentiation  potential.  The immunophenotypes of blast cells are usually consistent throughout the disease course even at relapse.  Rarely, blast cells may undergo a ‘lineage switch’ during the course of disease especially during relapse. We would like to highlight such  a  case in  a 10- year  old  boy  who  presented  with  a  two  weeks  history  of  lethargy,  poor  appetite,  low grade  fever,  respiratory  distress,  cardiac  failure,  generalized  oedema  and hepatosplenomegaly.  Full  blood  count  showed  a  leucocyte  count  of  41.5x109/L  and platelet  count  of  37x109/L.  The  peripheral  blood  film  showed  presence  of  numerous blast cells. Bone marrow aspiration revealed a hypercellular marrow, which consisted of mainly blast cells with high nuclear to cytoplasmic ratio and inconspicuous nucleoli. Immunophenotyping and cytochemistry results were consistent with the diagnosis of T- cell  acute  lymphoblastic  leukaemia.  The  patient  achieved  remission  after  treatment with  UK  ALL  97  protocol,  regime  B  chemotherapy.  However,  he  relapsed  seven months after the initial diagnosis with 26% blast cells in the bone marrow aspirate. The majority was L1 blast cells admixed with some L2 blast cells. Immunophenotyping was consistent  with  common  precursor  B  acute  lymphoblastic  leukaemia.  The  treatment was changed to a more lineage specific chemotherapy. Nonetheless, the patient never achieved remission and was planned for palliative management. This case illustrated a unique and rare case of rapid lineage switch from T-cell acute lymphoblastic leukaemia to common precursor B-cell acute lymphoblastic leukaemia.