What is tenosynovial giant cell tumour?

A benign but locally aggressive tumour of the synovium, the thin lining of joints, tendon sheaths and bursae. It does not spread to other parts of the body, but within a joint it can grow, bleed, erode bone and destroy cartilage. It most often affects people between roughly 20 and 50, which is a large part of why it is such a troublesome condition.

Is TGCT the same as PVNS?

Yes. Pigmented villonodular synovitis (PVNS) is the older name for the diffuse form inside a joint, and giant cell tumour of tendon sheath is the older name for the nodular form on a tendon. Tenosynovial giant cell tumour is now the umbrella term for all of them. If you have been told you have PVNS, this page is about your condition.

No. It does not metastasise and it does not threaten your life. It behaves badly in one place, which is a genuinely different problem from cancer, but not a trivial one. In an international registry of nearly 500 patients, almost a quarter had changed jobs or retired early because of the condition, which is a fair measure of how disruptive the diffuse form can be.

What is the difference between nodular and diffuse disease?

Nodular (localised) disease is a single discrete lump, often on a tendon of the hand or as one nodule inside a joint. Removing it usually deals with it. Diffuse disease involves the whole synovial lining of a joint (most often the knee) and behaves like a film rather than a lump, which is why it is difficult to remove completely and why it comes back so much more often.

Why does it keep coming back?

Because with diffuse disease the abnormal tissue coats the entire joint lining, including recesses at the back of the joint that are genuinely difficult to reach, and any left behind can regrow. In published series, recurrence after synovectomy for diffuse disease can exceed 50%, and in one knee series every patient whose tumour had eroded into bone recurred. Recurrence is not a sign the operation was done badly; it is the nature of this disease.

What is a synovectomy?

An operation to remove the synovial lining of the joint. It can be done arthroscopically through small incisions, as an open operation, or as a combination. An open approach is often needed to clear the back of the knee properly. For nodular disease only the involved area is removed; for diffuse disease the aim is to remove as much of the lining as possible.

Why would I need a knee replacement for a benign condition?

Two situations. First, long-standing diffuse disease can destroy the joint surfaces, so the joint itself is beyond saving even once the tumour is controlled. Second, clearing extensive disease sometimes requires removing the structures that normally stabilise the knee, and the replacement then has to provide that stability itself, which is why a more constrained implant, such as a rotating hinge, is sometimes used rather than a standard knee replacement.

Are there drug treatments for TGCT?

Yes. This is the area that has changed most. The tumour is driven by a chemical signal called CSF1, and drugs that block its receptor can shrink the tumour and improve pain, stiffness and movement. In a randomised trial, vimseltinib shrank tumours in 40% of patients against none on placebo. These medicines are used where surgery is unlikely to help or would cause real harm, and access varies between countries; it is a conversation for a specialist centre.

Will my joint be normal afterwards?

For nodular disease, usually close to it. For diffuse disease, honesty serves better. A joint that has had extensive synovectomy, sometimes more than once, is rarely a normal joint, and the aim of treatment is a joint that works and does not hurt, protected from further damage. That is also why treatment decisions in diffuse disease weigh long-term joint survival, not just removing tumour.

Tenosynovial giant cell tumour (PVNS)

Tenosynovial giant cell tumour (TGCT) is a benign tumour of the synovium, the thin membrane that lines joints, tendon sheaths and the small cushioning sacs around them. Benign here means it does not spread to other parts of the body. It does not mean harmless: the diffuse form is one of the most stubborn non-cancerous conditions in orthopaedics, and it mostly affects people in their twenties, thirties and forties.

A note on names, because this condition has several. The older terms are still widely used: pigmented villonodular synovitis (PVNS) for the diffuse form inside a joint, and giant cell tumour of tendon sheath for the nodule on a tendon. They are all the same disease family, now grouped as TGCT. If you have been given any of these names, this page is about your condition.

The essentials

It is not cancer. It does not spread and it does not shorten your life. Its damage is local, to the joint it lives in.
Nodular and diffuse are very different problems. A single nodule is usually cured by removing it. Diffuse disease coats the whole joint lining and can recur in more than half of cases after surgery.
The biology is unusual and matters to you: most of the lump is not tumour at all, but normal immune cells summoned by a chemical signal from a few abnormal cells. Drugs that block that signal now exist.
Surgery (synovectomy) remains the main treatment, tailored to how much of the joint is involved.
Diffuse disease in a young person is a long game. Decisions are made with an eye on what the joint will need over decades, not just on removing tumour today, and it is worth having that game plan made at a specialist centre.

One disease, four patterns

Two questions describe any TGCT, and together they set the treatment.

Where is it? Intra-articular disease is inside a joint: most importantly the knee, and also the hip and ankle. Extra-articular disease sits outside a joint, on a tendon sheath or in a bursa, classically as a firm nodule on a finger, where it is one of the commonest lumps of the hand.

How much of the lining is involved? Nodular (localised) disease is a single discrete lump. Diffuse disease involves the entire synovial lining, growing as fronds and sheets rather than a lump, staining the tissue rusty-brown with old blood, the “pigmented” of the old name.

The combinations behave differently: a nodule on a finger tendon is a minor operation with an excellent outlook; diffuse disease of the knee is a long-term condition needing a plan rather than a procedure. In a large surgical series the hand was the commonest site overall, with the knee third. But among diffuse cases, the knee dominates, and it is the diffuse knee that generates most of what follows on this page.

The biology: a small signal and a large crowd

TGCT has one of the more elegant explanations in tumour biology, worked out in 2006, and it is worth two paragraphs because everything about the new drug treatments follows from it.

Most of the cells in a TGCT are not tumour cells. Only a small minority carry the genetic abnormality: a rearrangement that switches on a gene called CSF1, making those cells continuously broadcast a chemical signal. CSF1 is the summons the immune system uses to recruit its housekeeping cells. So the abnormal cells call, and normal immune cells answer, in enormous numbers. The crowd, not the ringleaders, makes up the bulk of the tumour. Researchers called this a “landscape effect”: a few cells reshaping the whole neighbourhood.

This explains the disease’s behaviour (the swelling, the recurrent bleeding into the joint, the inflammation), and it handed medicine a target. If the tumour is a crowd assembled by one signal, blocking the signal’s receptor (CSF1R) should disperse the crowd. That is precisely what the new drugs do, and why a benign joint condition now has treatments borrowed from cancer medicine.

What it does to a joint, and why diagnosis is often late

Diffuse disease causes swelling, stiffness, pain and repeated episodes where the joint fills with blood-stained fluid. None of these is specific, and the condition is rare enough that it is often mistaken for meniscal problems, inflammatory arthritis or simple recurrent effusions. In an international registry of nearly 500 patients, half were misdiagnosed before the correct diagnosis was made, and a third waited more than two years from first symptoms.

The delay matters because the disease is not static. It erodes bone and wears cartilage: in a pooled analysis of hip disease (a joint with little room to spare), almost half of patients already had advanced cartilage damage at diagnosis, at a mean age of just 32. MRI is the investigation that makes the diagnosis, and the old blood pigment gives it a characteristic appearance that a musculoskeletal radiologist will recognise.

Surgery

Nodular disease: remove the nodule

For localised disease, excision of the nodule with its base is usually curative, whether on a finger tendon or as a single lesion inside the knee. Recurrence happens but is uncommon: across a large mixed series, about one in six patients overall, most of them re-operable.

Diffuse disease: synovectomy

For diffuse disease the operation is synovectomy: removing the diseased joint lining, as completely as can safely be done. Depending on the joint and the pattern of disease this may be arthroscopic (through small incisions), open, or both combined. In the knee, disease in the posterior compartments often needs an open posterior approach to clear properly, because the back of the knee hides exactly the recesses where arthroscopy struggles.

And here the honest number has to be said plainly: published recurrence rates for diffuse disease after synovectomy (arthroscopic or open) can exceed 50%. In a series of intra-articular knee TGCT, half of the diffuse cases recurred, and every patient whose tumour had eroded into bone recurred. Recurrence in this disease is not a verdict on the surgeon or the operation. It is the disease’s nature, it is why follow-up continues for years, and it is why diffuse TGCT should be managed somewhere that sees it repeatedly rather than occasionally.

When the joint is already destroyed: replacement, and the rotating hinge

Long-standing diffuse disease can bring a second problem: the joint surfaces themselves are worn out, by erosion, repeated bleeding and inflammation. At that point removing tumour is no longer enough, and joint replacement combined with synovectomy becomes the operation.

Knee replacement in this setting works (a systematic review found good clinical and functional results), but it differs from a routine knee replacement in two respects worth understanding:

The implant may need to be more constrained. A standard knee replacement relies on the patient’s own ligaments and capsule for stability. In extensive diffuse disease, clearing the tumour properly can mean removing much of that stabilising envelope, and the review of knee replacement in this condition found that with extensive joint involvement, implants with a higher degree of constraint were used to achieve a stable knee. The fullest version of that is a rotating hinge: an implant that links the two sides of the joint mechanically, substituting for the ligaments that have been sacrificed, while still allowing the knee to rotate as it bends. Using one is a planned decision that follows directly from how radical the synovectomy needs to be: the price of clearing the disease properly is an implant that no longer depends on what was removed.

The revision rate is higher than for ordinary arthritis. Replacements done for this condition are revised more often than those done for standard osteoarthritis: recurrence of the disease itself is the leading complication, followed by loosening and stiffness. That is not an argument against the operation; it is a reason it belongs in experienced hands, with follow-up that assumes the disease may not be finished.

The hard problem: diffuse disease in a young patient

Everything above converges on one genuinely difficult situation, and it deserves its own section because it is the conversation that matters most in clinic.

Diffuse TGCT most commonly affects people in their twenties to forties. A recurrence rate above 50%, in a disease that erodes joints, in a patient who may have sixty years of walking ahead of them, creates a set of competing pressures with no perfect answer:

Operating radically enough to control the disease can damage or destabilise a joint that needs to last decades.
Operating conservatively protects the joint today but concedes a high chance of recurrence and further surgery.
Replacing the joint solves the destroyed-surface problem, but a joint replacement in a 30-year-old is itself a decision with a long tail: implants wear, and each revision is harder than the last.
Doing little is not neutral either: the disease continues to bleed, erode and stiffen.

This is why diffuse TGCT in a young adult is not a single operation but a strategy: sequencing synovectomy, possibly drug treatment, and possibly eventual replacement in whatever order best protects the decades ahead. The registry finding that nearly a quarter of patients changed occupation or retired early because of this “benign” condition is the measure of what is at stake. It is also the strongest argument for having the strategy set at a specialist centre from the start, rather than arriving at one after the third recurrence.

The new medicines: blocking the signal

Because the tumour is a crowd assembled by the CSF1 signal, drugs that block the CSF1 receptor disperse it. Two have now been tested in randomised trials against placebo, in patients whose disease was not suitable for surgery, or where surgery would have caused real harm.

Vimseltinib, an oral tablet, was tested in the MOTION trial published in The Lancet in 2024: 123 patients, randomised, placebo-controlled, across 13 countries including Australia. Tumours shrank in 40% of patients on the drug and none on placebo, with improvements in movement, stiffness, physical function and pain. Side effects were mostly mild; the only severe laboratory change affecting more than one in twenty patients was a raised muscle enzyme. No serious liver injury of the kind reported with pexidartinib was seen in that trial, though a single trial of 123 patients cannot exclude rare harms.

Pexidartinib was the first drug approved (in the United States) for this disease. In final long-term trial results, around 60% of patients had their tumour shrink, most within six months, and responses were durable. Its important caveat is the liver: around one in three patients developed significantly abnormal liver tests, and rare cases of serious, even fatal, liver injury have been reported. In the United States it carries the regulator’s strongest boxed warning and is prescribed only within a liver-monitoring programme.

Two things to keep these in proportion. These drugs manage the disease rather than cure it: they suppress the crowd while the signal-sending cells remain. And their current place is where surgery is unlikely to help: unresectable disease, multiply recurrent disease, or disease where the operation would cost too much function. Whether giving them before surgery can shrink diffuse disease enough to make the operation safer and more complete is being actively explored, and early experience is promising but not yet proof. Availability differs between countries. Neither drug is in routine use in Australia at the time of writing, and access is a case-by-case discussion at a specialist centre, including whether a clinical trial is open.

What this means for you

If you have a single nodule (on a finger, or one lump in the knee), removal is usually the whole story.
If you have diffuse disease, think in terms of a long-term plan, not one operation. Ask what the strategy is for your joint over the next twenty years, not just for this admission.
A recurrence is not a failure, and it does not mean the situation is out of control. It is the known behaviour of this disease, and it is why your follow-up continues.
If a knee replacement is proposed, ask about the implant, and if a rotating hinge is recommended, understand it as the implant substituting for structures the disease (or its clearance) has taken, not as an inferior option.
Ask about the drug treatments if your disease has recurred, is inoperable, or surgery would cost you real function. They have changed this field in the last five years, and knowing they exist changes the conversation.
This condition will not shorten your life. The work is protecting the joint, and your function, for the long life you are going to have with it.

Assessment follows the usual pathway in tests and diagnosis, and treatment decisions in diffuse disease are made with the multidisciplinary team as set out in how treatment is planned. If you have been told you have PVNS or TGCT (particularly the diffuse form), a review at a unit that manages it regularly is worth arranging early, while the full range of options is still open.