Rhabdomyosarcomas are highly aggressive tumors that predominantly affect children .
They are also the sarcomas that have responded best to improvements in radiotherapy and chemotherapy. As a group, rhabdomyosarcomas are the most common sarcomas in childhood, representing more than half such cases. Alveolar rhabdomyosarcoma is commonly located in an extremity where it is first seen as a rapidly growing mass. Grossly, it appears to arise from within muscle. The diagnosis would be difficult without the use of modern immunopathological techniques such as use of peroxidase labeled antibodies to detect actin , a marker of skeletal muscle differentiation.