Type a thymoma staging is based on histologic analysis of thymoma. The current staging of thymoma includes histologic staging, TNM staging, and Masaoka staging, and the selection criteria for different staging varies. 1. Histologic staging: Thymoma can be divided into A-type thymoma and AB-type thymoma according to histologic analysis. A-type thymoma is mainly of medullary and spindle cell type, while AB-type thymoma usually refers to the mixed type. 2.TNM staging: according to TNM staging, T indicates tumor size and infiltration status, N indicates lymph node metastasis, and M indicates whether distant metastasis occurs. 3. Masaoka staging: Using Masaoka staging as the standard, thymoma is classified into stages I-IV. Stage I is confined to the peritoneum, stage II involves the mediastinum, stage III invades the pericardium, lungs, etc., stage IV invades the pleura, pericardium, etc., and stage V develops lymphatic and blood metastasis.