Tenosynovial giant cell tumors are rare tumors that form in the joints. TGCT can grow and damage surrounding structures, even though it is not typically cancer.

The tumors grow in three areas.

  • synovium: the thin layer of tissue that lines the inner joint surfaces
  • bursae: the fluid-filled sacs that cushion tendons and muscles around the joint to prevent friction
  • tendon sheath: a layer of tissue around tendons

TGCTs are divided into types based on where they are and how quickly they grow.

Localized giant cell tumors grow slowly. They start in smaller joints like the hand. These tumors are called giant cell tumors of the tendon sheath (GCTTS).

Large joints like the knee, hip, ankle, shoulder, and elbow are affected by giant cell tumors. The tumors are called pigmented villonodular synovitis.

There are two types of TGCTs found inside the joint. Giant cell tumors can be found outside the joint. They can spread to the lungs or the lymph nodes.

TGCTs are caused by a change to a chromosome, called a translocation. Pieces of a chromosome break off and change places. It isn’t clear what causes these translocations.

The genetic code for making the proteins is contained in chromosomes. The excess production of a colony-stimulating factor 1 is caused by the translocation.

White blood cells called macrophages are attracted to thisprotein by its ability to attract cells with the same CSF1 receptors. The cells clump together and form a tumor.

TGCTs often start in people who are in their 30s and 40s. The diffuse type is more common in men. These tumors are extremely rare: only 11 out of every 1 million people in the United States are diagnosed each year.

Which specific symptoms you get depends on the type of TGCT you have. Some common symptoms of these tumors include:

  • There is a lump in the joint.
  • The joint is stiff.
  • There is pain in the joint.
  • The skin is warm over the joint.
  • A sound when you move the joint.

Your doctor can possibly diagnose TGCT based on your symptoms and physical exam.

In addition, magnetic resonance imaging (MRI) will usually be necessary in order to see the lesion and determine the best surgical intervention.

Other tests may help with the diagnosis.

  • An X-ray.
  • A sample of fluid from the joints.
  • A sample from the joint.

Doctors usually remove the tumor and part of the synovium with TGCT. Some people who have this surgery have a tumor return. If this happens, you can have a second procedure to remove it.

Radiation therapy after surgery can destroy parts of the tumor that weren’t removable with surgery. You can get radiation from a machine outside your body, or straight into the affected joint.

Multiple surgeries are required in people with diffuse TGCT. The drugs called colony-stimulating factor 1 receptor (CSF1R) are used to stop the growth of tumors.

The only FDA-approved treatment for TGCT is pexidartinab.

The following are experimental. There is more research that needs to be done to confirm what benefit they have for people with TGCT.

  • cabiralizumab is a drug.
  • emactuzumab is a drug.
  • I amtinib is a drug used for cancer.
  • nilotinib is a drug.
  • Sunitinib is a drug.

Can a giant cell tumor turn malignant?

TGCTs are almost always benign. In rare cases, they may become malignant and could metastasize elsewhere in the body.

Is Tenosynovial giant cell tumor a sarcoma?

In the rare cases that a TGCT becomes cancerous, it does appear to become a sarcoma, according to a 2019 study of 10 cases.

Is giant cell tumor life threatening?

TGCTs are rarely life-threatening. However, they can be disabling and negatively affect a person’s quality of life.

TGCT can cause permanent joint damage and disability if it grows to the point where it is not usually cancer. In rare cases, the tumor can spread to other parts of the body and be life threatening.

If you have symptoms of TGCT, it is important to see your primary care doctor or specialist as soon as possible.