PAX3 and alveolar rhabdomyosarcoma: These changes can be grouped in sarcomas with simple karyotypes and specific genetic alterations [such as EWS RNA binding protein 1 (EWSR1) fusions in Ewing sarcoma, paired box 3 (PAX3) fusions in alveolar rhabdomyosarcomas, among others] and in sarcomas with complex genetic modifications [7].