The conventional nested RT-PCR and/or karyotype method detected 240 rearrangements in the 319 patients with leukemia at diagnosis: 61 PML-RARa, 39 RUNX1-RUNX1T1, 32 CBFB-MYH11, 4 MLLT3-MLL, 1 DEK-NUP214, 61 BCR-ABL1, 12 MLL rearranged, 14 TEL-AML1, and 16 TCF3-PBX1. The gene discussed is TCF3; the disease is leukemia.