EWSR1 and Ewing sarcoma: The 2020 World Health Organization (WHO) classification of tumors of soft tissue and bone introduced a dedicated chapter for undifferentiated small round cell sarcomas, encompassing Ewing sarcoma and three newly recognized subtypes: round cell sarcomas with EWSR1:non-ETS fusions, CIC-rearranged sarcoma, and sarcomas with BCOR genetic alterations [7].