First, in FISH-diagnosed KMT2A (MLL gene, 11q23)/AFDN (AF6, 6q27)-rearrangement, RNA-sequencing identified an unknown CCDC32 (15q15.1)/CBX3 (7p15.2) gene fusion in both newly diagnosed and relapsed samples, which is previously unknown in KMT2A/AFDN-rearranged AML patients. Here, CBX3 is linked to acute myeloid leukemia.