Chronic Myeloid Leukemia, BCR-ABL1 Positive

BCR-ABL1-positive chronic myeloid leukemia is a clonal neoplasm of abnormal pluripotent bone marrow stem cells. The hallmark cytogenetic abnormality, t(9;22)(q34;q11), produces BCR-ABL1 gene, and that not only plays a critical role in pathogenesis but also provides an excellent target for therapy with various tyrosine kinase inhibitors and a surveillance marker for disease activity and progression. With understanding the molecular pathophysiology and development of tyrosine kinase inhibitors, BCR-ABL1-positive chronic myeloid leukemia turns from a universally fatal disease to a medically manageable disorder. This chapter summarizes the diagnostic criteria for different phases of diseases (chronic, accelerated, and blast), the definitions of different levels of responses (hematologic, cytogenetic, and molecular), and the strategies of monitoring therapeutic responses (conventional karyotyping, FISH, real-time quantitative reverse transcription polymerase chain reaction, and kinase domain mutation detection).