<prompt> Commonest sarcoma in children is -RhabdomyosarcomaLipomaAngiosarcomaFibrosarcoma  <response>: RhabdomyosarcomaCommonest sarcoma in children is rhabdomyosarcoma.It is a tumour of Primitive mesodermal origin.The most common site is head and neck.The genitourinary region is the second most common site.Other sites are extremities and retroperitoneum 