MPL and primary myelofibrosis: In addition, the JAK2-V617F mutation is detected in approximately 50–60 % of patients with essential thrombocythemia (ET) and primary myelofibrosis (PMF) (Baxter et al. 2005; James et al. 2005; Kralovics et al. 2005; Levine et al. 2005; Campbell and Green 2006), and activating mutations of the myeloproliferative leukemia virus oncogene (MPL) are present in 5–10 % of patients with ET or PMF without the JAK2-V617F mutation (Pikman et al. 2006; Rumi et al. 2013).