CRLF2 rearrangements (P2RY8/CRLF2 and IGH/CRLF2) and mutations (CRLF2 F232C) lead to CRLF2 overexpression, which may be detected by flow cytometry, and these mutations are present in approximately half of BCR/ABL1-like ALL cases, being more commonly seen in patients with Native American ancestry. The gene discussed is CRLF2; the disease is acute lymphoblastic leukemia.