JAK2 and myeloproliferative neoplasm: BCR-ABL1-neg MPN patients frequently carry somatic mutations of Janus kinase 2 (JAK2) tyrosine kinase, with JAK2-V617F identified as the most prevalent variant that induces overactivation of JAK/STAT signaling and its downstream pathways, which is also observed in MPNs driven by other mutations in JAK2, MPL, and CALR (Pasquier et al., 2014).