STAT5B and T-cell large granular lymphocyte leukemia: Other sequencing studies have revealed somatic activating mutations in JAK3 (A572V and A573V) in 38% of NKTCL, STAT3 and STAT5B in T-LGL, and recurrent gain-of-function mutations in JAK2 and STAT3 in AITL [5, 8, 42, 53].