STAT5B and T-cell large granular lymphocyte leukemia: As regards STAT5B mutations, among the 82 cases with clonal T/NK-LGLs investigated here, only one mutation at the SH2 domain of STAT5B was identified (Y665F-mutation, 1% of the whole series) in a TCD4+-LGLL patient (1/14 TCD4+-LGLL; 7%).