<prompt> Which is the most common site of rhabdomyosarcoma?OrbitNasopharynxExtremitiesHypopharynx  <response>: The most common primary sites for RMS are the head and neck paicularly orbit and parameninges 35, the genitourinary tract 22, and extremities 18. Rhabdomyosarcoma is the most common primary malignant tumor of the orbit in childhood. It is most common soft tissue sarcoma in childhood. It arise from tissue resembling striated muscle, which contain rhabdomyoblasts or primitive muscle cells. 