A rare type of cancer that forms in cartilage or other soft tissue but not in bone. It usually occurs in the head and neck. Most extraskeletal mesenchymal chondrosarcomas are fast-growing and may spread to other parts of the body. They may also recur (come back) many years after treatment. Extraskeletal mesenchymal chondrosarcoma usually occurs in young adults. It is a type of soft tissue sarcoma.