Wu et al. (53) described a child with B-ALL who experienced two relapses with short event-free intervals; cytogenetic analysis at diagnosis identified the t(12; 21) translocation causing ETV6::RUNX1 fusion, but molecular genetic testing at the second relapse revealed a concurrent interstitial deletion of chromosome X leading to P2RY8::CRLF2 fusion (54). Here, CRLF2 is linked to acute lymphoblastic leukemia.