What Are Tenosynovial Giant Cell Tumors?

A guide to understanding the different types of this rare disease, and the different terms associated with it.

Tumors are abnormal growths of tissue. Tenosynovial giant cell tumors, or TGCTs, are a rare type of tumor that occurs in the tissues in and around the joints, such as the synovium bursae and tendon sheath. Though typically benign—meaning they are not cancerous—TGCTs can cause pain, swelling, and stiffness in the affected joints, and in some cases, joint damage and disability. This disease is most common in adults between the ages of 25 and 40, though TGCTs can affect people of any age.

Because TGCTs are rare, finding information can be challenging for patients. Adding to that challenge is the fact that different types of TGCTs have been known by different names over the years, and the different terminology can be confusing.

Below is an overview of the main types of TGCTs, as well as a look at some of the other names and terms that may be used to describe the different types of TGCTs.

Types of TGCTs

The World Health Organization classifies TGCTs into two main subtypes: pigmented villonodular synovitis (PVNS) and giant cell tumor of the tendon sheath (GCTTS). While there are several differences between the two, the key terms to understand are localized and diffuse.

Localized refers to an injury or disease that is confined to a specific area. Diffuse refers to an injury or disease that is spread over a wider area. With TGCTs, localized means a single mass or growth that affects one part of a joint, while diffuse means an abnormal growth pattern occurring in tissue throughout the joint.

GCTTS is typically localized, while PVNS follows a diffuse growth pattern (PVNS is also known as “diffuse-type giant cell tumor”).

There are other differences as well. While either type could occur in joints throughout the body, GCTTS most often occurs in smaller joints (such as the joints in the hands) while PVNS most commonly occurs in the knee or other larger joints (such as the hip or shoulder). GCTTS is more common. PVNS is more aggressive, and more likely to cause joint damage and disability, especially if left untreated.

PVNS is also more likely to recur after treatment. Surgery to remove the tumors is the most common treatment for both PVNS and GCTTS. Radiation therapy is sometimes used when all of a tumor cannot be removed through surgery. There are also several medications that are under development for the treatment of TGCTs.

Other terms to know

As mentioned above, there have been a few names given to the different types of TGCTs over the years, and some of these names are still in use or may show up when you are looking for information on this rare disease. Additionally, there are other terms used to describe different TGCTs.

  • Intra- and extra-articular: TGCTs are further classified as being intra-articular (occurring inside the joint) and extra-articular (occurring outside the joint).
  • Localized PVNS: This is a previously used name for intra-articular types of GCTTS.
  • Nodular tenosynovitis: This is a previously used name for extra-articular types of GCTTS.
  • Diffuse-type PVNS: This is a previously used name for PVNS.
  • Diffuse-type giant cell tumor: Mentioned above, this is another name for PVNS, and is still in use.
  • Diffuse tenosynovial giant cell tumor: Also another name for PVNS, and also still in use.
  • Malignant TGCT: This is a very rare occurrence where a malignant cancer occurs alongside TGCT, or TGCT recurs after treatment in the form of a malignant tumor.

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