Small deletions are common in B‐ALL, often seen with CRLF2 rearrangements and inactivating mutations of the JAK/STAT (IL7R, FLT3, SH2B3, JAK1, and JAK3) or RAS signaling pathways (NF1, KRAS, PTPN11, and BRAF). Here, CRLF2 is linked to acute lymphoblastic leukemia.