Moreover, somatic STAT3 and STAT5b mutations determining constitutive activation have been reported, the former detected in a proportion of approximately 40% of patients [10, 11] and the latter being associated to aggressive LGL disorders [12] and, as recently reported, to CD4+ T-LGL leukemia patients (6 out of 11 cases) [13]. This evidence concerns the gene STAT5B and T-cell large granular lymphocyte leukemia.