EWSR1 and Ewing sarcoma: Ewing's sarcomas result from chromosomal translocations that generate dominant transforming fusion proteins of the transactivation domain of the EWS protein with the ETS domain of one of the five Ets proteins Etv1, Etv4, Erg, Fli1, and Fev (Fifth Ewing Variant, PET-1) (20, 21).