Phrenic nerve paralysis from recurrence of stage I thymoma with myasthenia gravis 10 years after complete resection

A 34-year-old woman underwent thymo-thymectomy for myasthenia gravis (MG) and was diagnosed with type B3 Masaoka stage I thymoma. Phrenic nerve paralysis developed 8 years after surgery, and a left-sided mediastinal mass was seen on a chest radiograph 10 years after surgery. Chest computed tomography revealed a tumor measuring 57 × 21 × 28 mm beside the aortic arch. Surgical resection of the tumor with partial resection of phrenic and recurrent nerve, the left upper lobe, and the pericardium was performed through a left thoracotomy. Histological examination confirmed recurrent thymoma invading the resected surrounding organs. The patient received radiation therapy postoperatively and was alive with stable symptoms of MG at the 2-year follow-up. Symptomatic relapse of thymoma is very rare and an occult recurrent thymoma should be considered in patients with unilateral phrenic nerve paralysis even after complete resection of thymoma. Detailed examination with careful follow-up should be considered.