Detection of thymoma in myasthenia gravis.

Twenty patients with myasthenia gravis had chest radiography, conventional tomography, and computed tomography (CT) of the thorax within 1 month of thymectomy. Four of the six macroscopic tumors were detected on routine chest radiography; conventional tomography provided no additional information. CT detected all six macroscopic tumors and provided additional information that was not available by other procedures. However, 18 patients (90%) had anterior mediastinum densities on CT, which could not be distinguished preoperatively from thymic tumors. All six patients with macroscopic tumors had serum antistriational muscle antibody titers; this test was negative in 10 of 11 patients (91%) without thymoma. Chest radiography, CT of the thorax, and antistriational antibodies are the tests recommended for detection of a thymoma in patients with myasthenia gravis.