Approximately 50% of patients with Ph-like ALL harbor rearrangements of the cytokine receptor- like factor 2 (CRLF2) gene, located on the pseudoautosomal region 1 (PAR1) of chromosomes Xp22 and Yp11 [4,12,15,24]. The gene discussed is CRLF2; the disease is acute lymphoblastic leukemia.