Is a big scar left after thymectomy?

Not always: Many thymectomies can be done minimally invasively with small incisions and a high definition camera.

Not necessarily: Thymectomy used to be done through a large scar: e.g. Splitting the sternum as is done for open heart surgery. Recently, however, some thoracic surgeons have been doing some thymectomies endoscopically, which leaves a much smaller scar.

Not necessarily: Modern, well trained thoracic surgeons can perform thymectomy by vats or robotic technique on appropriate candidates. Sternotomy is not routinely required for thymectomy. This link may help: http://goo.Gl/3xxmd.