A 56-year-old woman with malignant thymoma lived for 19 years after diagnosis and died of superior vena cava syndrome. An autopsy showed invasion of the thymoma to the right lung and metastasis to the left lung. The pathologic diagnosis was epithelial thymoma (spindle cell dominant) accompanied with pure red cell aplasia (PRCA). However, this was well controlled with steroid therapy. She was the longest survivor with malignant thymoma at this time. Her long-term survival may be the result of good control of the PRCA.