Deletion of the IKZF1 gene was detected in 2 (3.8%) of 53 patients with available DNA sample of diagnostic leukemic blasts, which was a significantly lower frequency than that of pediatric BCP-ALL patients without TCF3-PBX1 fusion (3.8% vs. 10.4%, P < 0.001, Table 4). The gene discussed is PBX1; the disease is acute lymphoblastic leukemia.