STAT5B and T-cell leukemia: The primary objective of this study was to understand the structural, genomic, and pathophysiological impacts of two human leukemic STAT5B mutations (Rajala et al, 2013; Kiel et al, 2014), STAT5BY665F and STAT5BY665H, identified in patients with T-cell leukemias (Rajala et al, 2013; Kiel et al, 2014).