Some pediatric renal tumors have an undifferentiated “small round blue cell” appearance, such as blastemal WTs, MRTKs, as well as tumors that rarely involve or infiltrate the kidney, such as (poorly differentiated/undifferentiated) neuroblastoma, desmoplastic small round cell tumor (DSRCT), and Ewing sarcoma (EWS) (Table S2). Here, EWSR1 is linked to desmoplastic small round cell tumor.