RESUMO
A 46-year-old man was diagnosed as malignant thymoma, and was treated with chemotherapy and radiotherapy in 2003. On June 2004, he had edema of his legs and nephrotic syndrome (NS). As renal biopsy revealed a minor glomerular abnormality, he was diagnosed as minimal change nephrotic syndrome (MCNS). Intravenous steroid therapy of 500 mg/day for 3 days, following oral administration of 15 mg/day prednisolone and 75 mg cyclosporine twice a day was taken from July 2004. On July 2005, he went into remission of NS with 0.6 g/day proteinuria. On January 2008, NS relapsed with left pleural effusion. Chest CT and a biopsy specimen from left pleural mass lesion revealed the pleural invasion of malignant thymoma. Sixty Gray radiotherapy diminished the pleural metastatic lesion and also improved proteinuria from 6.6 g/day to 0.4 g/day. Though there have been a few case reports of MCNS concomitant with malignant thymoma, this is the first report that radiotherapy for metastatic malignant thymoma improved NS while diminishing the tumor.