53/65 (82%) in the B-ALL group had cytogenetic changes such as t(9;22) (n = 18), 9p abnormality (n = 12), t(1;19) TCF3-PBX1 gene fusion, (previously called E2A-PBX1) (n = 3) and a range of other abnormalities, including Burkitt lymphoma, hyperdiploidy, hypodiploidy, monosomy 7 and 12p abnormality (n = 20). This evidence concerns the gene TCF3 and Burkitt lymphoma.