alveolar rhabdomyosarcoma (al-VEE-oh-ler RAB-doh-MY-oh-sar-KOH-muh)
A soft tissue tumor that is most common in older children and teenagers. It begins in embryonic muscle cells (cells that develop into muscles in the body). It can occur at many places in the body, but usually occurs in the trunk, arms, or legs. Also called ARMS.