<prompt> The staging system for thymoma was developed by:MasaokaYokohamaTodaniKluive  <response>: The staging system for thymoma was developed by Masaoka The stage is increased on the basis of the degree of invasiveness. The 5-year survival in stage I, 96; stage II, 86; stage III, 69; stage IV, 50. The French Study Group on Thymic Tumors GETT has modified the Masaoka scheme based on the degree of surgical removal. Ref: Harrison, E-18, chapter e-20. 