Validation of the latest WHO histological classification and the 8th TNM staging system for thymic epithelial tumors

Histological classification and staging systems are indispensable for performing accurate management and research in patients with malignant tumors. The World Health Organization (WHO) classification and the Union for International Cancer Control (UICC) tumor-node-metastasis (TNM) classification are the international standards for the histological classification and staging of malignant tumors. However, for thymic epithelial tumors (TETs), these systems were not available until 1999 (1) and 2017 (2), respectively, perhaps because of the rarity and unique biological behavior of these tumors.