Notably, this residue is most frequently mutated in STAT5B (Asn642His) and has been reported in multiple cancer phenotypes (>150 cases [41,62,69,77,80,81,83,84,85,86,87,88,89,90,91,92,93,94,95,96,97,98,99,100,101,102]), most commonly T-cell-prolymphocytic leukemia (T-PLL), monomorphic epitheliotropic intestinal T-cell lymphoma (MEITL), and T-cell acute lymphoblastic leukemia (T-ALL). This evidence concerns the gene STAT5B and T-cell prolymphocytic leukemia.