Many cancers are driven by fusion proteins that undergo phase separation, such as EWS-FLI1 in Ewing sarcoma, SS18-SSX1 or SS18-SSX2 in synovial sarcoma, PAX3-FOXO1 in rhabdomyosarcoma, and NUP98-HOXA9 in acute myeloid leukemia (AML)10, 11. Here, SS18 is linked to Ewing sarcoma.