Masaoka staging system of thymoma

Last revised by Yuranga Weerakkody on 15 May 2022

The Masaoka staging system is commonly adopted for thymomas 1-3, and is the most important determinant of survival following surgical resection 4:

  • stage I: intact thymic capsule
  • stage II: capsular invasion into adjacent mediastinal fat or pleura
  • stage III: macroscopic invasion into adjacent organs, vessels
  • stage IV
    • IVa: dissemination in thoracic cavity (i.e. pleural or pericardial implants) 
    • IVb: distant metastases

Stage II and above are regarded as thymic carcinoma 2.

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Cases and figures

  • Case 1
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  • Case 2: stage I
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