In most cases, they can be distinguished from lymphoma (leucocyte common antigen, B and T markers) and embryonal rhabdomyosarcoma (muscle specific actin, desmin).
An antibody directed at the alpha and gamma isoforms of actin, which are present in smooth and striated muscle, produced a distinct positive staining in all the alveolar and embryonal rhabdomyosarcomas and in 8/18 small and dark cell malignancies, 7 of which were also shown to express desmin.