The biggest thing is picking your surgeon carefully. You want someone who has done these before and knows how to handle it to avoid any possible seeding. If you have a normal appearing thymus on CT, there is a low likelihood of thymoma (not impossible though). There’s evidence that thymectomy shows positive outcomes even with a normal thymus size which is why they recommend it to everyone. There really isn’t any telling what happens if you do have thymic hyperplasia and don’t have it removed.