CT of benign soft-tissue masses of the extremities.

The computed tomographic (CT) scans and medical records of 35 patients with proven benign soft-tissue masses of the extremities were reviewed to assess the contribution of CT in the evaluation of such masses. CT demonstrated the mass in all 35 cases and was able to provide a specific diagnosis in 28 (80%); 25 prospectively, three retrospectively. Correct diagnoses made using CT included hematomas (five), synovial cysts (seven), myositis ossificans (six), fatty tumors (four), aneurysms (three), pseudoaneurysms (two), schwannoma (one), and abscess (one). The CT appearance of a hematoma depends on its age. Synovial cysts are near-water-density masses, often associated with a small joint effusion. Myositis ossificans can be differentiated from parosteal osteosarcoma by virtue of its characteristic zonal ossification. Lipomas are recognized on noncontrast scans by the characteristic low attenuation of fat, while aneurysms and pseudoaneurysms are best diagnosed on postcontrast scans. In seven cases (20%) a specific diagnosis could not be made on the basis of the CT scan. However, in these cases CT delineated the extent of the mass and demonstrated its relation to surrounding structures; this anatomic information was helpful in planning surgical excision or percutaneous biopsy. The authors conclude that CT is a valuable noninvasive imaging method for the evaluation of soft-tissue masses of the extremities.