Malignant Solitary Fibrous Tumor, from the CureRays guide library.

Malignant solitary fibrous tumor is the aggressive form of a usually-benign fibrous tumor that can grow almost anywhere in the body; it is treated with surgery and radiation and watched closely because it can recur or spread many years later.

What it is.

Solitary fibrous tumor is a soft-tissue tumor that arises from fibrous (connective) tissue and can appear almost anywhere — the lining of the lungs (pleura), the abdomen and pelvis, the limbs, the head and neck, or the lining of the brain (where it was once called hemangiopericytoma). Most solitary fibrous tumors are benign and cured by surgery, but a subset are malignant: they grow faster, have more dividing cells under the microscope, and can both come back locally and spread to distant organs such as the lungs, liver, and bone. All solitary fibrous tumors, benign or malignant, share the same molecular signature — a NAB2-STAT6 gene fusion — which pathologists detect with a STAT6 stain to confirm the diagnosis. A key feature of even the malignant form is that recurrence or spread can happen very late, sometimes a decade or two after the original tumor, so lifelong follow-up matters.

How radiation treats it.

Radiation damages the DNA inside tumor cells so they can no longer divide, while healthy tissue repairs itself. In malignant solitary fibrous tumor, radiation lowers the risk of the tumor returning after surgery and, as precise radiosurgery or SBRT, can control tumors on the lining of the brain or individual metastases. It is given as short, painless daily sessions (or a few sessions for radiosurgery) and leaves no radioactivity in your body, so you stay safe to be around family throughout treatment.

The ways we can treat it.

Intensity-modulated / image-guided radiation (IMRT/IGRT). Precisely shaped x-ray beams deliver a high dose to the tumor bed while protecting nearby organs, useful given how varied these tumors' locations are.

Stereotactic radiosurgery / SBRT. Highly focused, high-dose beams in one or a few sessions treat meningeal tumors and individual lung or bone metastases with millimeter precision.

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

Questions we hear often.

My tumor was called a solitary fibrous tumor — is it cancer? Most solitary fibrous tumors are benign and cured by surgery. Yours is the malignant form, which means it has features that make recurrence or spread more likely, so it's treated more thoroughly — usually surgery plus radiation — and followed closely.

Why do I need follow-up for so long? Solitary fibrous tumors are well known for coming back or spreading very late — sometimes 10 to 20 years later. Long-term imaging lets your team catch any recurrence early, when it can often be treated with surgery or focused radiation.

Is this the same as the old 'hemangiopericytoma'? Yes. Tumors once called hemangiopericytoma — especially those on the lining of the brain — are now recognized as solitary fibrous tumors because they share the same NAB2-STAT6 gene fusion. The change reflects better understanding, not a different disease.

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