Moreover, our results provide further evidence of the correlation between STAT5b mutations and CD4+ T-LGL leukemia, recently described in a small cohort of cases (n = 11) and here confirmed in a larger cohort of patients (n = 33) even if with a lower incidence (15.2% vs 55% reported [13]). Here, CD4 is linked to T-cell large granular lymphocyte leukemia.