Presentation
Slowly progressive left knee swelling for 2 years. Off & on pain, aggravating with long distance walking. No history of trauma, fever, skin color changes or discharge.
Patient Data
Mild suprapatellar soft tissue swelling/knee joint effusion. No bone fracture or dislocation is seen. Articular surfaces are intact.
Findings: Moderate to large synovial effusion showing villi form synovial proliferation with septations and multiple nodules. Some areas show hemosiderin deposition and other areas subacute hemorrhagic components. Some erosions and bone marrow edema are seen in the posterior lateral femoral condyle. Some bone edema is also seen in the patella. No articular destruction is seen.
A well-defined lesion measuring 3.2 x 4.3 x 3.3 cm, containing variable abnormal signal intensities, is seen along the posterior aspect of the lateral femoral condyle. Cruciate ligaments, menisci and medial collateral ligament are intact.
Impression: Imaging findings are suggestive of pigmented villonodular synovitis, however, possibility of synovial neoplastic process cannot be excluded.
Case Discussion
Procedure: Left knee arthroscopy and synovial biopsy (5 months after the MRI). Microscopic description: Focal chronic arthritis and nodular collection of mononuclear cells admixed with multinucleated giant cells & hemosiderin pigment deposition. Diagnosis: Pigmented villonodular tenosynovitis. Negative for malignancy.
Procedure: Arthroscopic synovectomy (9 months after the synovial biopsy). Diagnosis: Tenosynovial giant cell tumor (diffuse type). Tumor size: 6.5 cm (ex vivo). Tumor involves inked/cauterized margins. Negative for malignant transformation.