PVNS/TGCT

For Medical Students

What It Shows

Pigmented villonodular synovitis, now usually called tenosynovial giant cell tumour, is a benign proliferative tumour of synovium. 5.5.11 covers the synovium.

It carries haemosiderin, which produces low signal on every sequence and signal loss on gradient echo images. 5.2.18 covers the gradient echo imaging.

It matters because that signature separates it from everything else in this chapter, and because the diffuse form recurs. 5.14.1 covers synovitis.

How It Is Acquired

Use a gradient echo sequence, because the iron's effect is the diagnostic finding. 5.2.18 covers the gradient echo imaging.

Use a T1 weighted and a fluid sensitive sequence to show the nodular tissue against the fluid. 5.2.13 covers the T1 imaging.

Decide whether the disease is localised or diffuse, since the two behave differently. 5.5.11 covers the synovium.

Map the extent, including the posterior compartment and any extension outside the capsule. 5.4.4 covers the posterior knee.

Assess the bone for erosion where nodules press on it. 5.5.6 covers the bones.

What Normal Looks Like

A thin synovial lining with no nodules. 5.5.11 covers the synovium.

No signal loss on gradient echo images. 5.2.18 covers the gradient echo imaging.

No erosion at the capsular attachments. 5.5.6 covers the bones.

A posterior compartment free of soft tissue mass. 5.4.4 covers the posterior knee.

What Abnormal Looks Like

Nodular synovial tissue with low signal on T1 weighted and fluid sensitive sequences alike. 5.2.13 covers the T1 imaging.

Signal loss on gradient echo images, which is the iron. 5.2.18 covers the gradient echo imaging.

A single localised nodule, often anterior, which is the localised form. 5.5.11 covers the synovium.

Diffuse involvement of the whole lining, the posterior compartment included. 5.4.4 covers the posterior knee.

Erosion of bone beside nodules, which is pressure rather than invasion. 5.5.6 covers the bones.

MRCS Level

How It Is Acquired

In a viva the expected answer names the signal signature.

The expected points are the gradient echo sequence, the low signal on all sequences, the localised or diffuse distinction, the extent, and the bone.

Say that this is the only condition here with a specific magnetic resonance signature. 5.14.1 covers synovitis.

Say that the extent on imaging decides the operation. 5.5.11 covers the synovium.

Say that the diffuse form recurs, so the follow-up is imaging rather than discharge. 5.20.7 covers reporting the post-operative knee.

What Abnormal Looks Like

The reasoning expected is that repeated small haemorrhages leave iron in the tissue, and iron disturbs the local magnetic field, which is why the signal is low everywhere and is lost fastest on a gradient echo sequence. 5.2.18 covers the gradient echo imaging.

That makes the sequence choice decisive, because a study without a gradient echo sequence can describe nodular synovitis without naming it. 5.5.1 covers the standard protocol.

The localised form is excised and usually does not return, while the diffuse form involves the whole lining including the posterior compartment, which is why complete excision is difficult. 5.4.4 covers the posterior knee.

Extension outside the capsule changes the approach and is the part most often under-reported. 5.20.8 covers common reporting errors.

How Good It Is

Magnetic resonance imaging is the best available test for this tumour and is the only one in this chapter where the appearance names the disease.

Its best contribution is the signature, the distinction between localised and diffuse, and the extent. 5.2.18 covers the gradient echo imaging.

It is limited because the signature needs the right sequence, because haemosiderin follows repeated bleeding of any cause, and because the posterior extent is easy to understate. 5.4.4 covers the posterior knee.

No figures appear for accuracy on this page, under decision 028, and no lesion dimensions or recurrence rates appear either: those are published quantities from particular series and this environment cannot check them.

FRCS Level

How Good It Is

At decision level the imaging decides the operation's extent and its approach. 5.5.11 covers the synovium.

A localised anterior nodule is an arthroscopic excision. 5.14.1 covers synovitis.

Diffuse disease with posterior involvement needs the posterior compartment addressed, which the approach has to allow for. 5.4.4 covers the posterior knee.

Extracapsular extension takes the operation beyond the joint. 5.13.7 covers bone tumours.

Bone erosion and cartilage loss decide whether the joint is salvageable at all. 5.3.17 covers joint space narrowing.

Where It Misleads

The commonest error is reporting the tumour as synovitis because no gradient echo sequence was acquired. 5.2.18 covers the gradient echo imaging.

Haemosiderin from repeated haemarthrosis is read as this tumour. 5.14.1 covers synovitis.

The posterior extent is understated because the field of view or the attention stopped anteriorly. 5.4.4 covers the posterior knee.

Pressure erosion is read as malignant invasion. 5.13.7 covers bone tumours.

A localised nodule is reported as a loose body. 5.14.6 covers synovial chondromatosis.

Fellowship Level

Where It Misleads

At fellowship level the disease has usually been excised once and the question is recurrence. 5.20.7 covers reporting the post-operative knee.

Post-operative haemosiderin and scar produce the same low signal as residual tumour, so the first post-operative scan is a baseline rather than an answer. 5.2.18 covers the gradient echo imaging.

That makes the pre-operative extent the single most valuable record, and it is often not transferred with the patient. 5.20.1 covers structured reporting.

Diffuse disease in a joint with cartilage loss raises whether excision is still the right operation. 5.3.17 covers joint space narrowing.

Metabolic imaging has been used to assess activity in these tumours and is rarely available. 5.18.7 covers the PET-MRI.

The useful report gives the signature, the form, the full extent with the posterior compartment named, any extracapsular component, and the state of the joint. 5.20.1 covers structured reporting.