ABL1 and chronic myelogenous leukemia, BCR-ABL1 positive: For example, Nowell and Hungerford [4] used cytogenetic methods in 1960 to first describe the Philadelphia chromosome, which underpins chronic myeloid leukemia (CML); however, thirteen years elapsed before the Philadelphia chromosome was identified as the product of a translocation between chromosomes 9 and 22 [5], and the translocation was finally revealed to cause a fusion between the BCR and ABL genes in 1985 [6].