Somatic JAK3 GOF mutations have also been identified in cancers affecting other hematopoietic cell lineages, such as acute megakaryoblastic leukemia (AMKL) [32,33,34], juvenile myelomonocytic leukemia (JMML) [35] and B cell precursor acute lymphoblastic leukemia (BCP-ALL) [36]. Here, JAK3 is linked to acute lymphoblastic leukemia.