• ) The age of the subjects on the day of signing the informed consent was ≥ 18 years old and \< 75 years old, regardless of gender ;

• ) Chest thin-layer CT and MR showed anterior mediastinal space-occupying lesions, combined with relevant hematological indicators, the patient was clinically diagnosed as a thymic epithelial tumor with or without myasthenia gravis ( MG ) symptoms.

• ) need to accept thymectomy surgery ;

• ) Clinical stage I to IIIA ( AJCC-UICC TNM staging system ) ;

• ) The maximum diameter of the lesion \< 5cm ;

• ) physical condition score 0 or 1 ( Eastern Cooperative Oncology Group ECOG scoring system ) ;

• ) Have not received any anti-thymoma therapy before, including but not limited to systemic chemotherapy, radiotherapy, etc. ;

• ) Preoperative major organ function meets the following criteria : Bone marrow function: hemoglobin ≥ 10.0 g / dL ( no blood transfusion within 28 days before hemoglobin examination ), absolute neutrophil count ≥ 1.5 × 109 / L, platelet count ≥ 100 × 109 / L ( no transfusion of apheresis platelets or IL-11 treatment within 14 days before platelet count examination ) ; coagulation function : INR and PT \< 1.5 × ULN, APTT ≤ 1.5 × ULN ; liver function: transaminase ( ALT and AST ) ≤ 2.5 × ULN; total bilirubin ≤ 1.5 × ULN ( Gilbert's syndrome or liver metastasis subjects total bilirubin ≤ 2.5 × ULN ) ; renal function: serum creatinine clearance rate ≥ 60 mL/min ( calculated according to the Cockcroft-Gault formula ) ;

• ) voluntarily participated in and were able to undergo robot-assisted or thoracoscopic thymectomy, and complied with the study follow-up plan.