JAK2 and acute lymphoblastic leukemia: The ETV6::JAK2 (ETS variant transcription factor 6/JAK2) fusion (initially known as TEL::JAK2) was the first JAK2r identified by cytogenics in both ALL and CML patients 1997 and was the first JAK2 alteration demonstrated to induce constitutive activation of JAK2 (Lacronique et al., 1997; Peeters et al., 1997; Raivola et al., 2021).