Oncologist can help. A pediatric oncologist is needed to decide what to do with a soft tissue sarcoma. Whether the sarcoma is slow growing and low grade, or bad and aggressive, can sometimes vary from teen to teen. The nonrhabdomyosarcoma soft tissue sarcomas (nrstss) are about 4% of childhood cancers. Many names include dermatofibrosarcoma protuberans, synovial sarcoma, alveolar soft part sarcoma, fibrosarcoma, etc..