KMT2A and leukemia: For example, synovial sarcoma (SS) harbors a hallmark onco-fusion termed SS18::SSX (6, 7), while the infantile, pediatric, and childhood leukemias frequently carry the onco-fusion involving lysine methyltransferase 2A [KMT2A, also known as mixed lineage leukemia 1 (MLL1)] (2, 8) and nucleoporin 98 (3).