A microthymoma and no germinal centre in myasthenia gravis.

A 43-year-old woman with a 1-year history of generalized myasthenia gravis was referred for a video-assisted thorascopic surgery thymectomy. The preoperative chest computed tomography revealed mild diffuse thymic hyperplasia. Pathology of the resected thymus gland revealed a 6-mm World Health Organization (WHO) Type AB microthymoma without thymic germinal centres. The entity of microthymoma was reviewed with a focus on examining the pathological and therapeutic differences between thymic hyperplasia and microscopic thymoma.