All patients with CRLF2‐r were B‐ALL (n = 172): IGH‐CRLF2 (n = 47) and P2RY8‐CRLF2 (n = 125), median age 5 years (range 1–60 y), male predominance (59%), 70% had WBC <50 × 106/l (Supporting Information Table 4; Figure 1A). Here, CRLF2 is linked to acute lymphoblastic leukemia.