Extraskeletal Myxoid Chondrosarcoma, from the CureRays guide library.

Extraskeletal myxoid chondrosarcoma is a rare, slow-growing soft-tissue sarcoma — not a true bone or cartilage cancer despite its name — that is controlled with surgery and radiation but tends to recur and spread very late.

What it is.

Despite its name, extraskeletal myxoid chondrosarcoma is not really a cartilage cancer and does not arise in bone. It is a distinct soft-tissue sarcoma, usually found as a deep lump in the thigh or other large muscles of the limbs in middle-aged adults. 'Myxoid' refers to the jelly-like material that fills the tumor. It is defined by a characteristic gene rearrangement — most often NR4A3 (also called CHN/TEC) fused to a partner gene such as EWSR1 — which pathologists use to confirm the diagnosis, since it can be mistaken for other myxoid tumors. Its behavior is unusual: it usually grows slowly and patients often live a long time, yet it has a high tendency to come back locally and to spread to the lungs, sometimes a decade or more after the original tumor was treated. That makes complete removal and very long-term follow-up essential.

How radiation treats it.

Radiation damages the DNA inside cancer cells so they lose the ability to divide, while normal tissue repairs itself and recovers. In extraskeletal myxoid chondrosarcoma, radiation is used around surgery to reduce the strong tendency for the tumor to return locally, and as precise SBRT to destroy individual lung metastases. Treatment is delivered as a series of short, painless daily sessions (or a few sessions for SBRT) and leaves no radioactivity in your body, so you remain safe to be around others throughout.

The ways we can treat it.

Intensity-modulated / image-guided radiation (IMRT/IGRT). Sculpted, image-guided x-ray beams deliver a high dose to the tumor or surgical bed while sparing nearby skin, bone, and joints to preserve limb function.

Stereotactic body radiation therapy (SBRT). Very precise, high-dose beams from many angles can ablate individual lung metastases in a few sessions, a good fit for this tumor's slow, oligometastatic spread.

Proton therapy (selected cases). Protons can reduce dose to surrounding tissue for tumors near the spine, pelvis, or other sensitive structures.

Questions we hear often.

Is this a bone or cartilage cancer? No — despite the word 'chondrosarcoma' in its name, it is a soft-tissue sarcoma that arises in muscle and other soft tissues, not in bone or true cartilage. The name reflects its appearance under the microscope, not its origin or behavior.

Why do I need follow-up for so many years? This tumor is famous for coming back or spreading to the lungs very late — sometimes 10 years or more after treatment. Long-term scans let your team catch and treat any recurrence early, often with surgery or precise radiation.

If it spreads to my lungs, is treatment hopeless? Not at all. Because spread is often slow and limited to a few spots, individual lung tumors can be removed or ablated with focused radiation, and many patients live well for years even with metastatic disease.

This guide is informational only. It is not medical advice — please confirm anything here with your care team.