Rearrangements involving cytokine receptor-like factor 2 (CRLF2) gene (CRLF2r) have been identified in approximately 10 % of pediatric BCP-ALL [15], but their incidence increases to approximately 50 % in children with Philadelphia-like (Ph-like) BCP-ALL [16], and in Down syndrome (DS)-associated BCP-ALL [17,18]. The gene discussed is CRLF2; the disease is acute lymphoblastic leukemia.