Giant Cell Tumour of Tendon Sheath

Giant cell tumour of tendon sheath is a noncancerous growth that forms in the soft tissue around your joints, most commonly affecting the fingers, hands, and feet. While not dangerous, these slow-growing lumps can cause pain and stiffness, and may return even after treatment.

Table of contents

• What is Giant Cell Tumour of Tendon Sheath?
• Who Gets This Condition?
• Signs and Symptoms
• What Causes This Tumour?
• How It Is Diagnosed
• Treatment Options
• What to Expect

tenosynovial giant cell tumor, GCTTS, GCT-TS

What is Giant Cell Tumour of Tendon Sheath?

Giant cell tumour of tendon sheath is a benign tumour, which means it is not cancerous and cannot cause cancer^[1]. These tumours develop in the soft tissue around your joints, specifically in the tendon sheath—the protective sleeve that surrounds and protects your tendons^[1]. Tendons are the strong cords that connect your muscles to your bones.

This condition is the second most common tumour of the hand, with only simple ganglion cysts being more common^[3]. The tumour was first described by a doctor named Chassaignac in 1852, who mistakenly called them “cancers of the tendon sheath” because he overestimated how dangerous they were^[3].

• Fingers and thumbs
• Hands and wrists
• Ankles and feet
• Knees
• Elbows

Giant cell tumours can be classified into two main types: localized and diffuse^[5]. The localized form is more common and typically affects small joints like those in your fingers. It grows slowly and stays in one area^[3]. The diffuse form is rare and can grow more quickly, sometimes spreading beyond the original area^[3].

Who Gets This Condition?

Anyone can develop a giant cell tumour of tendon sheath, but certain groups of people are more likely to develop this condition^[1]. The tumour most commonly affects women and adults between the ages of 30 and 50^[1]. However, these tumours can occasionally occur in young children^[12].

Giant cell tumours of tendon sheath are very rare overall. Fewer than 50 in every 1 million people worldwide develop these tumours each year^[1]. According to research, there are approximately 29 cases per million of localized tumours affecting fingers and toes, 10 cases per million in other locations, and 4 cases per million of diffuse tumours^[10].

Signs and Symptoms

The most common way this condition appears is as a noticeable bump or lump on your hand, finger, or foot^[1]. Many people have these lumps for a long time—sometimes months to years—before they seek medical attention^[4]. The tumour is usually a painless, slow-growing, firm mass^[3].

Common symptoms include^[1]:

• A visible bump or lump
• Pain that gets worse when you move the affected area
• Swelling around the tumour

You may also experience symptoms in the joint near the tumour^[1]:

• A catching, locking, or popping feeling when you move your joint
• Heat or warmth on the skin around your joint
• Stiffness in the joint
• Your joint feeling unstable or weak
• Decreased range of motion^[12]

Although these tumours typically cause no symptoms aside from occasional numbness in the affected finger or toe, mild disability may result if the tumour impairs the functioning of the digit^[3]. In some cases, the tumour can put pressure on nearby bones and cause bone damage that appears as indentations on X-rays^[4].

What Causes This Tumour?

The exact cause of giant cell tumours of tendon sheath is unknown^[1]. Several theories have been proposed over the years, including trauma, disturbed fat metabolism, infection, blood vessel problems, immune system issues, inflammation, and metabolic disturbances^[3].

The most widely accepted explanation is that these tumours result from a reactive or regenerative overgrowth associated with an inflammatory process^[3]. Recent research has found evidence that the cells in these tumours resemble osteoclasts—cells that normally break down bone tissue—suggesting they come from a type of white blood cell called a monocyte or macrophage^[3].

Some studies have found a link between people who develop these tumours and certain changes in their chromosomes, which are the parts of your cells that contain your DNA^[1]. Specifically, experts think a translocation—when some chromosomes break apart and reconnect in new pairs—may cause these tumours^[1]. These chromosomal abnormalities cause an overproduction of a protein called CSF-1, which leads cells to clump together and form a tumour^[12].

How It Is Diagnosed

Your healthcare provider will diagnose a giant cell tumour of tendon sheath using a combination of physical examination, imaging tests, and tissue analysis^[1].

During the physical exam, your doctor will examine the lump and ask about your symptoms, including how long the lump has been present and whether it causes pain or limits movement^[4].

Imaging tests help your doctor see the tumour and surrounding structures. Common imaging tests include^[3]:

• X-rays: These may show changes in nearby bones, such as indentations caused by pressure from the tumour. However, radiological changes are seen in only some cases^[4].
• Magnetic Resonance Imaging (MRI): This test provides detailed images of soft tissues and can help determine the size and extent of the tumour^[3].
• Ultrasound: This test uses sound waves to create images and can help visualize the tumour^[3].

Fine Needle Aspiration Cytology (FNAC) is an important diagnostic tool that involves taking a small sample of cells from the tumour using a thin needle^[4]. This test can help confirm the diagnosis before surgery. Some surgeons suggest that having this diagnosis available helps them take appropriate precautions during surgery^[4]. However, FNAC may be inconclusive in some cases^[4].

Final confirmation of the diagnosis comes from examining the removed tumour tissue under a microscope, which reveals the characteristic appearance of giant cells and other cell types^[3].

Treatment Options

The main treatment for giant cell tumour of tendon sheath is surgical removal of the tumour^[1]. However, there are now also medication options for certain cases.

Surgery

Surgical removal (called marginal excision) has traditionally been the treatment of choice for these tumours^[3]. The goal of surgery is to completely remove the tumour along with any small satellite nodules that may be nearby^[4].

Several factors contribute to successful surgery^[4]:

• Pre-operative planning with tissue diagnosis using fine needle aspiration
• Wide surgical exposure to see the entire tumour
• Meticulous dissection using magnification (operating microscope or magnifying loupe) to ensure complete removal of all tumour tissue and satellite nodules^[4]

The tumour may involve the tendon sheath, the plate of tissue on the palm side of the finger joint, capsular ligaments, and joints^[8]. Sometimes the surgeon needs to temporarily remove or move nearby structures to completely remove the tumour^[8].

Surgery is not recommended for patients who have poor overall health or life-threatening illnesses^[3].

Medications

For patients where surgery would cause severe problems or for tumours that have come back multiple times, medication options are available^[8].

In 2019, the U.S. Food and Drug Administration approved a drug called pexidartinib (brand name Turalio) for treating these tumours^[8]. This was the first systemic therapy approved for this condition. Pexidartinib works by blocking a protein receptor called CSF1R, which prevents the activation of substances that cause inflammation^[8]. By stopping inflammatory cells from producing certain chemicals, the drug is thought to stop tumour cells from growing.

In clinical trials, 38% of patients treated with pexidartinib showed improvement at week 25, compared with 0% of patients who received a placebo^[8]. Among those who responded, most maintained their response for 6 months or longer. However, the drug can cause liver problems, so the dose was later adjusted to reduce this risk^[8].

In February 2025, another drug called vimseltinib was approved for treating symptomatic tumours in adult patients where surgery would cause severe functional limitations or morbidity^[8]. Vimseltinib also works by blocking CSF1R and showed a 40% response rate in clinical trials^[8].

Radiation Therapy

Some patients may need radiation therapy in addition to surgery^[1], particularly if the tumour has come back multiple times.

What to Expect

The main concern with giant cell tumours of tendon sheath is that they can come back (recur) after treatment. Recurrence is an unresolved issue even though the condition is not dangerous^[4].

For localized tumours treated with surgery, the recurrence rate is generally low when the tumour is completely removed^[5]. However, the diffuse form of the tumour is more difficult to treat with surgery and has a high recurrence rate^[5]. In one study of 14 patients followed for an average of 4.3 years, only one case showed recurrence, which was successfully managed with a second surgery^[4].

Several factors have been suggested as increasing the risk of recurrence, including proximity to the end joints of fingers, presence of degenerative joint disease, pressure erosions visible on X-rays, and increased cell division activity^[4]. However, the only consistent factor found by various researchers for preventing recurrence is complete surgical removal with elimination of all satellite nodules^[4].

People who have had a giant cell tumour of tendon sheath are more likely to develop rheumatoid arthritis or osteoarthritis in the affected joint^[1]. If left untreated, the diffuse form may cause arthritic damage and degeneration to the joint and surrounding cartilage and bone^[14].

With proper diagnosis and careful surgical technique using magnification, most patients can expect a good outcome with a low risk of recurrence^[4]. Regular follow-up with your healthcare provider is important to monitor for any signs that the tumour has returned.