CRLF2 and acute lymphoblastic leukemia: It is clear from our data that CRLF2‐r ALL is heterogeneous, requiring a combination of genetic abnormalities in functionally relevant genes to co‐operate with deregulated expression of CRLF2. Although the functional relevance of some of the deletions and mutations presented in this descriptive study are currently unknown, there are pointers to activation of additional targetable pathways.