A poorly circumscribed morphologic variant of rhabdomyosarcoma. It is characterized by the presence of primitive skeletal muscle differentiation in any stage of myogenesis. The disease is MONDO_0009993 (embryonal rhabdomyosarcoma). Also known as: ERMS, embryonal rhabdomyosarcoma (disease), rhabdomyosarcoma, embryonal, type 1, rhabdomyosarcoma, somatic.