Estimated frequency of specific genotypes in childhood ALL. Data were modified from Pui et al⁹  by including recently identified genotypes. The genetic lesions that are exclusively seen in cases of T-cell ALL are indicated in gold and those commonly associated with precursor B-cell ALL in blue. The darker gold or blue color indicates those subtypes generally associated with poor prognosis. BCR-ABL1–like cases can be separated into one group with CRLF2 dysregulation and the other with activating cytokine receptor and kinase signaling.