Soft tissue sarcomas are a group of rare cancers that develop in tissues like muscle, fat, blood vessels or deep skin tissues. The most common soft tissue sarcomas in adolescents and young adults are undifferentiated pleomorphic sarcoma, myxofibrosarcoma and synovial sarcoma. A diagnostic plan involves imaging tests, biopsy and pathology review to determine the type and stage of cancer. Treatment typically involves surgery along with radiation and/or chemotherapy depending on the cancer's stage and grade.