Definition

A rare, slow-growing type of cancer that forms in soft tissues outside the bone and usually has certain changes in the NR4A3 gene that cause abnormal fusion proteins to be made. EMCs usually occur in the thigh but may also occur in the knee, buttock, or chest and abdomen. They may grow large and spread to nearby tissue or to other parts of the body, especially the lungs. They may also come back many years after treatment. EMCs usually occur in middle-aged or older adults and are rare in children and adolescents. They are a type of soft tissue sarcoma. Also called extraskeletal myxoid chondrosarcoma.