The new classifications for thymic epithelial tumors: benefits and problems

The tumor-node-metastasis (TNM) classification for cancer is a globally accepted principle used by oncologists. It provides planning treatments, indication of prognosis, evaluating the outcomes of treatments, facilitating the exchange of information between institutions, and facilitating the continued investigation of human cancers (1). For thymic epithelial tumors, the Masaoka classification was published in 1981 (2), and Koga et al. modified this classification in 1994 (3). This Masaoka-Koga classification has been widely used for a long time.