Understanding Tenosynovial Giant Cell Tumor (TGCT)

Health Article
Tenosynovial Giant Cell Tumor (TGCT)

Understanding Tenosynovial Giant Cell Tumor (TGCT)

What is Tenosynovial Giant Cell Tumor (TGCT)?

Tenosynovial Giant Cell Tumor (TGCT) refers to a rare group of tumors that primarily develop in joints and surrounding tissues. While TGCTs are generally benign, their growth can lead to significant damage to nearby structures and cause discomfort.

Areas Affected by TGCT

These tumors typically arise in three key regions within the joint:

  • Synovium: The delicate membrane that lines the interior of joints.
  • Bursae: Fluid-filled sacs that act as cushions for tendons and muscles, minimizing friction around joints.
  • Tendon Sheath: The protective casing surrounding tendons.

Types of TGCT

TGCTs are classified based on their location and growth behavior:

  • Localized Giant Cell Tumors: These tumors grow slowly and are commonly found in smaller joints, particularly in the hands. They are referred to as Giant Cell Tumors of the Tendon Sheath (GCTTS).
  • Diffuse Giant Cell Tumors: These tumors grow at a faster rate and typically affect larger joints such as the knee, hip, ankle, shoulder, or elbow. This category includes conditions known as Pigmented Vilonodular Synovitis (PVNS).

Both localized and diffuse types of TGCT can be present inside the joint (intra-articular), and diffuse tumors may occasionally appear outside the joint (extra-articular). In exceptional situations, they may also metastasize to areas like the lymph nodes or lungs.

What Causes TGCT?

The primary cause of TGCT is a chromosomal alteration known as translocation, where sections of chromosomes break and reattach irregularly. Although the precise triggers for these translocations remain unidentified, they result in the overproduction of a protein known as Colony-Stimulating Factor 1 (CSF1).

This excessive CSF1 production attracts immune cells with CSF1 receptors, particularly macrophages. These cells aggregate and form a tumor over time. TGCT commonly presents in individuals in their 30s and 40s, with a higher prevalence in men for diffuse types. Despite their rarity—affecting only about 11 individuals per million in the U.S. annually—TGCT requires careful diagnosis and management.

Identifying Symptoms

The symptoms of TGCT may vary depending on the type. Common indicators include:

  • Swelling or the presence of a lump in the joint
  • Joint stiffness
  • Pain or tenderness in the affected area
  • Increased warmth over the joint
  • Joint noises such as locking, popping, or catching during movement

How is TGCT Diagnosed?

Diagnosis of TGCT typically begins with a thorough evaluation of symptoms and a physical examination by a healthcare provider. Magnetic Resonance Imaging (MRI) is commonly employed to visualize the lesion and ascertain the most suitable surgical approach.

Additional diagnostic tests may include:

  • X-ray imaging
  • Analysis of synovial fluid from around the joint
  • Tissue biopsy from the joint

Treatment Options for TGCT

The primary treatment for TGCT is surgical removal of the tumor, which may involve excision of part or all of the synovium. In some cases, tumors may recur after surgery, necessitating further intervention.

Post-surgical radiation therapy can help target remaining tumor cells, and treatment can be administered either externally or directly into the joint.

Patients with diffuse TGCT may experience recurrent tumors, leading to multiple surgeries over time. In such instances, colony-stimulating factor 1 receptor (CSF1R) inhibitors are being investigated to limit tumor cell aggregation.

The only FDA-approved treatment for TGCT is pexidartinab (Turalio), with several CSF1R inhibitors currently under research:

  • Cabiralizumab
  • Emactuzumab
  • Imatinib (Gleevec)
  • Nilotinib (Tasigna)
  • Sunitinib (Sutent)

Common Questions About TGCT

Can TGCT become malignant?

While TGCTs are predominantly benign, instances of malignant transformation do occur, although these cases are rare.

Is TGCT classified as a sarcoma?

In rare instances of malignancy, TGCT may indeed display characteristics consistent with sarcomas, as noted in studies.

Is TGCT life-threatening?

Generally, TGCTs are not life-threatening; however, they can significantly impair quality of life and may lead to disability.

Final Thoughts

While TGCT is not typically malignant, its potential to cause irreversible joint damage and related disability is significant. In rare cases, TGCT can metastasize, underscoring the importance of prompt diagnosis and treatment. If you are experiencing symptoms suggestive of TGCT, consult with your healthcare provider or a specialist for evaluation and management.