 9/26/96: Repetitive stimulation studies of the median, facial, and spinal accessory nerves showed no evidence of decrement at baseline, and at intervals up to 3 minutes following exercise. The patient had been off Mestinon for 8 hours prior to testing. Chest CT with contrast, 9/26/96, revealed a 4x2.5x4cm centrally calcified soft tissue anterior mediastinal mass adjacent to the aortic arch. This was highly suggestive of a thymoma. There were diffuse emphysematous disease with scarring in the lung bases. A few nodules suggestive of granulomas and few calcified perihilar lymph nodes. He underwent thoracotomy and resection of the mass. Pathologic analysis was consistent with a thymoma, lymphocyte predominant type, with capsular and pleural invasion, and extension to the phrenic nerve resection margin. Acetylcholine Receptor-binding antibody titer 12.8nmol/L (normal<0.7)