In an effort to define genetic lesions that cooperate with BCR-ABL1 to transform to Philadelphia chromosome positive acute leukemia, Mullighan et al. [65] studied 304 cases of ALL, including 23 CML cases with a 250K Affymetrix SNP array, and found only 0.47 copy number alterations per case in chronic phase CML (range 0–8), which suggested that chronic phase CML is genomically stable and BCR–ABL1 is sufficient to induce CML. Here, BCR is linked to chronic myelogenous leukemia, BCR-ABL1 positive.