[Case report: Tenosynovial giant cell tumor arising from the knee joint].

Giant cell tumor of the tendon sheath and synovium or pigmented villonodular synovitis of the tendon is a benign neoplasm, although there are rarely reported malignant metastatic forms. The most common location is the hand. Large joints such as the ankle and knee are infrequently affected. Diagnosis might be suspected radiologically, but the exact diagnosis has to be confirmed by histopathologic examination. In this study, we report MRI findings of three giant cell tumors of the tendon sheath.