Mutations in JAK2 can lead to leukaemia and lymphoma.[1] Specifically, mutations in exons 12, 13, 14 and 15 of the JAK2 gene are proposed to be a risk factor in developing lymphoma or leukemia.[5] Additionally, mutated STAT3 and STAT5 can increase JAK-STAT signalling in NK and T cells, which promotes very high proliferation of these cells, and increases the likelihood of developing leukaemia.[2] Also, a JAK-STAT signalling pathway mediated by erythropoietin (EPO), which usually allows the development of red blood cells, may be altered in patients with leukemia.[62]