A Case of Simultaneously Operated Primary Multiple Lung Cancers with Non-thymomatous Myasthenia Gravis

Background. Cases of lung cancer with myasthenia gravis (MG) have rarely been reported. Case. A 76-year-old woman had been complaining of ptosis and muscle weakness of the lower limbs. She received an injection of edrophonium chloride which resulted in improvement of muscle strength. We diagnosed sero-negative MG. Chest X-ray demonstrated an abnormal shadow in the right upper lung field. Chest computed tomography showed 3 lesions, a 3-cm mixed ground glass opacity (GGO) in the right S1 segment, a 1-cm GGO in the right S3 segment and a 5-mm GGO in the left S10 segment. She simultaneously underwent extended thymectomy and radical right upper lobectomy with regional lymph node dissection through a median sternotomy without intercostal incision. Histological examination revealed that the lesions of the S1 and S3 segment were mixed adenocarcinoma and bronchioloalveolar carcinoma respectively. The postoperative course was uneventful, and the patient was transferred to the Department of Neurological Medicine for medication of MG on the tenth day after operation. The patient is alive without any signs of recurrence 50 months later, GGO of the left S10 segment has not changed, and her strength has remained almost normal with pyridostigmine bromide. Conclusion. We report a case of simultaneously operated primary multiple lung cancers with non-thymomatous myasthenia gravis. It is important to keep the rare possibility of lung cancer associated with MG in mind.