Giant cell tumor of the tendon sheath: MR findings in nine cases.

OBJECTIVE: The purpose of this study was to determine the MR findings in patients with giant cell tumors of the tendon sheath. MATERIALS AND METHODS: MR imaging findings in nine surgically proved cases of giant cell tumors of the tendon sheath were evaluated on both T1- and T2-weighted images. Of nine lesions, three involved the foot, two involved the thumb, two involved the knee, one involved the proximal part of the tibia, and one involved the proximal part of the femur. RESULTS: All nine lesions were hypointense on T1-weighted images; the signal intensity of most of the tumors was approximately equal to that of skeletal muscle. On the T2-weighted images, three lesions were hypointense relative to skeletal muscle, two lesions were approximately isointense relative to skeletal muscle, and two lesions were slightly hyperintense relative to skeletal muscle but hypointense relative to fat. The remaining two lesions had a more heterogeneous appearance on T2-weighted images. CONCLUSION: On both T1- and T2-weighted images, giant cell tumor of the tendon sheath has a signal intensity similar to that of its pathologic counterpart, pigmented villonodular synovitis. The decreased signal intensity on both T1- and T2-weighted images is an uncommon appearance of extraarticular soft-tissue masses, in particular when they occur in the hands or feet, and this may suggest the diagnosis of giant cell tumor of the tendon sheath.