TCF3-PBX1 is one of these fusions and is found in 3–6% of BCP-ALL patients; moreover, the acquisition of secondary genomic aberrations, such as loss of CDKN2A/B, PAX5 or RB1, is common and crucial to leukemogenesis in those cases [1, 2]. The gene discussed is PBX1; the disease is acute lymphoblastic leukemia.