STAT5A and chronic myelogenous leukemia, BCR-ABL1 positive: STAT3 and STAT5 are aberrantly tyrosine‐phosphorylated in cancer cells and are crucial effectors of different tyrosine kinase oncogenes (TKO) such as FLT3‐ITD in acute myeloid leukaemia (AML) and BCR‐ABL in CML.25, 26