Unusual clinical behaviour of thymoma with recurrent myasthenia gravis.

A 58-year old man with thymoma and myasthenia gravis (MG) had undergone thymectomy 8 years ago with histopathologically confirmed non-invasive WHO-type AB thymoma. After 5 years of complete remission, symptoms of MG resurfaced, and a recurrent anterior mediastinal mass was detected for which he received radiotherapy. He presented to us 3 years later with productive cough and exertional dyspnoea; the positron emission tomography-computed tomography scan revealed a metabolically active pulmonary nodule in the right lung as the only site of disease for which a right lower lobectomy was done. Microscopy established an intrapulmonary WHO-type B2 thymoma and the patient is currently asymptomatic on steroids, anticholinesterase and immunosuppressant therapy. We discuss the variable and unpredictable course of thymomas; the possibility of transformation into more aggressive types with each recurrence, association with recurrent MG post-thymectomy and presentation several years later with metastatic disease.