CRLF2 and leukemia: Many studies have been limited to specific subtypes of leukemia or risk groups or have relied solely on the MLPA assay, which does not detect all CRLF2 (CRLF2r) or DUX4 (DUX4r) rearrangements, and may overcall IKZF1 alterations by including those cases with aneuploidy of chromosome 7 (7).