Ikaros is also an important tumor suppressor in human B-cell precursor acute lymphoblastic leukemias (BCP-ALL) [7–9], with a high frequency of loss-of-function mutations in cases with activated STAT5-dependent oncogenic pathways, like BCR-ABL translocations, CRLF2 amplifications or JAK2 activating mutations [10–12]. The gene discussed is STAT5A; the disease is neoplasm.