Extraskeletal myxoid chondrosarcoma

Extraskeletal myxoid chondrosarcoma (EMC) is a rare soft tissue sarcoma that, despite its name, arises outside of bone and does not typically produce true cartilage. It is classified as a malignant mesenchymal neoplasm and is considered a distinct entity separate from conventional skeletal chondrosarcoma. EMC most commonly presents as a slow-growing, painless mass in the deep soft tissues of the proximal extremities (especially the thigh), although it can also occur in the trunk, retroperitoneum, and rarely in other locations. The tumor is characterized by a multinodular architecture with abundant myxoid (gelatinous) matrix and cords or clusters of small, round to slightly elongated tumor cells. EMC predominantly affects adults, with a peak incidence between the ages of 40 and 60, and shows a male predominance. The disease is genetically characterized by recurrent chromosomal translocations, most commonly t(9;22)(q22;q12), which results in the EWSR1::NR4A3 fusion gene. Other variant translocations involving NR4A3 with different partner genes (such as TAF15 or TCF12) have also been described. While EMC tends to grow slowly, it has a significant propensity for local recurrence and late distant metastases, particularly to the lungs, soft tissues, and lymph nodes. The long-term prognosis is guarded, with metastatic disease developing in a substantial proportion of patients over extended follow-up periods. Treatment of extraskeletal myxoid chondrosarcoma primarily involves wide surgical excision with clear margins, which remains the cornerstone of therapy. Radiation therapy may be used as an adjunct, particularly when surgical margins are close or positive, or in cases of locally advanced disease. EMC is generally considered resistant to conventional chemotherapy, although some responses have been reported with certain regimens. Targeted therapies and clinical trials are being explored for advanced or metastatic disease. Due to the risk of late recurrence, long-term surveillance with imaging is recommended for all patients following treatment.

Inheritance

Sporadic

Usually appears on its own, not inherited from a parent

Age of Onset

Adult

Begins in adulthood (age 18 or older)

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Source: NORD Rare Disease Centers + NIH Undiagnosed Diseases Network (UDN) · centers verified active within last 12 months

Source: PubMed + NIH RePORTER + openFDA + clinical-journal RSS · last 30 days · disease-tagged at ingest by AI extraction with human QC

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