As described above, the MLPA platform is widely used by several groups to identify focal DNA copy number alterations and the “IKZF1plus” composite genotype, but this platform is not an adequate surrogate for sensitive detection of several key subtypes: e.g., ERG deletion in DUX4-rearranged ALL (only ~50% of cases have clonal ERG deletion), and PAR1 deletion in CRLF2-rearranged ALL (IGH-CRLF2 is usually not accompanied by PAR1 deletion). The gene discussed is CRLF2; the disease is acute lymphoblastic leukemia.