JAK2 and plasma cell myeloma: Following identification of JAK2 p. V617F in 2005 (Baxter et al., 2005; James et al., 2005; Kralovics et al., 2005; Levine et al., 2005), an array of other JAK2 mutations have been identified in MPNs, myeloma, lymphoma, and chronic and acute leukaemias of either myeloid or lymphoid lineage (Lee et al., 2006; Krämer et al., 2007; Furqan et al., 2013; Vainchenker and Constantinescu, 2013; Fasouli and Katsantoni, 2021; Raivola et al., 2021).