Orthopaedic Oncology cases PVNS
A 38-year-old female presents to the emergency room with knee pain and swelling that began this morning when she woke up. She denies recent trauma. Over the past 6 months, this has occurred several times, and she has had frank blood aspirated from her knee at an urgent care center. She denies fever, chills, or pain in other joints. An MRI is conducted in the emergency room, which is displayed below in Figure 8–45A and B.
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Figure 8–45 A–B
What is the most likely diagnosis?
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Medial meniscus tear
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Pigmented villonodular synovitis
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Septic arthritis
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ACL tear
Discussion
The correct answer is (B). Recurrent atraumatic hemarthroses in one joint is suggestive of PVNS. This benign tumor of synovium creates low signal on T1 and T2, illustrated in these images. Injuries to both the medial meniscus and ACL would be evident on the MRI, and neither of these findings is shown in the image. She has no signs or symptoms of septic arthritis, which usually is associated with aspiration of purulent fluid, not bloody fluid.
What is the molecular mechanism that leads to the development of PVNS?
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t(1;2) translocation leading to CSF1-COL6A3 fusion product
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t(11:22) translocation leading to the EWS-FLI1 fusion product
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17q11.2 defect
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EXT1 and EXT2 gene abnormality
Discussion
The correct answer is (A). The underlying pathologic molecular mechanism for PVNS has recently been elucidated. A specific t(1;2) translocation fuses the colony stimulating factor-1 (CSF1) gene to the collagen type Via3 (COL6A3) promoter, leading to the attraction of non-neoplastic inflammatory cells expressing the CSF1 receptor. The t(11;22) translocation leads to Ewing sarcoma; the 17q11.2 defect leads to neurofibromatosis type 1, and the EXT1 or EXT2 genetic defects leads to multiple hereditary exostoses.
The patient’s MRI reveals diffuse PVNS. What is the recommended treatment?
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Observation and symptomatic treatment with NSAIDs
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Total knee arthroplasty
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Total synovectomy
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Chemotherapy and radiation
Discussion
The correct answer is (C). The standard of care for the diffuse form of PVNS is total synovectomy, often via an anterior and posterior approach. Eventually, these patients may require total knee replacement due to chondral erosion from recurrent tumor. This patient does not have any arthritis at this point, therefore arthroplasty would be premature. There is no role for NSAIDs or radiation in treating this condition. Medical therapies are on the horizon, currently in clinical trials since the underlying molecular mechanism of this disease has been defined.
Objectives: Did you learn...?
Mechanism of development of PVNS? Treatment of PVNS?