Pigmented villonodular synovitis

Case contributed by Dr Henry Knipe

Presentation

Left lower limb swelling for three days.

Patient Data

Age: 45
Gender: Female
X-ray

Well corticated erosions are seen in both of the posterior tibia and posteromedial fibular proximally associated with a linear periosteal reaction. Impression of a large soft tissue mass posterior to the knee. 

Nuclear medicine

99mTc MDP

Consistent with a tumour in the proximal left tibia where there is focally increased activity. Elsewhere no abnormalities are detected.

A large lesion is seen in the left popliteal fossa formed by conglomeration of two masses. Superiorly it is at the level of gastrocnemius attachment, inferiorly it extends to proximal fibular shaft level. There is intra-articular extension into the posterior knee joint space and proximal tibiofibular joint. 

Below the knee it causes large paraarticular bony erosions/oedema in the proximal tibia and fibula, occupies the deep flexor compartment, extends through the interosseous membrane into the deep extensor compartment. It is  related to soleus muscle. The lesion is hypointense on T1, with thin strands of enhancement seen throughout and surrounding it.

The patient proceeded to CT guided core biopsy

MACROSCOPIC DESCRIPTION: "L popliteal mass Bx": Three 2mm diameter pale tan core biopsies 5-20mm long. 

MICROSCOPIC DESCRIPTION: The core biopsies contain a densely cellular infiltrate, comprising many mononuclear cells as well as some multinucleated giant cells. They all have similar morphology with mildly enlarged nuclei and occasional conspicuous nucleoli. Many of the mononuclear cells contain refractile haemosiderin deposits in the cytoplasm. There are  intermixed lymphocytes, foamy macrophages and occasional eosinophils in the background. No abnormal mitoses are seen. There is no necrosis. The overall features are those of pigmented villonodular synovitis. There is no evidence of malignancy.

DIAGNOSIS: Left popliteal mass biopsy: Pigmented villonodular synovitis.

Case Discussion

Pigmented villonodular synovitis (PVNS) is a rare benign proliferative condition affecting synovial membranes of joints, bursae or tendons. A key features is haemosiderin deposition and gradient echo (GRE) can be very helpful if performed. 

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Case information

rID: 40257
Case created: 15th Oct 2015
Last edited: 19th Dec 2015
Inclusion in quiz mode: Included

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