Chronic Myelogenous Leukemia (CML) is a hematologic cancer characterized by the proliferation of myeloid cells

 Under normal conditions, these cells develop into neutrophils, eosinophils, and basophils, and the increased cells have a characteristic specific chromosomal abnormality, namely a translocation between chromosome 9 and chromosome 22. This is an exchange of segments between chromosome 9 and chromosome 22. Chromosome 9 has a lengthened tip of its long arm, while chromosome 22 becomes shorter. We call this segment of chromosome 22 the Philadelphia chromosome (Philadelphia, Ph chromosome). The translocation produces a hybrid gene from the BCR-ABL1 gene on the Ph chromosome. This hybrid gene activates the function of other proteins on its own without waiting for commands from the cell, causing an increase in the number of cells that the body does not need. This hybrid gene can also halt DNA repair, so that abnormal genes are not repaired, leading to an increasing number of abnormalities in other genes. CML is divided into 3 types: chronic phase, accelerated phase, and blast crisis.