Tumor-Node Metastasis Staging System for Thymic Epithelial Tumors

Background:The Masaoka clinical staging classification is the most widely accepted nowadays and is an excellent predictor for the prognosis of thymoma. Nevertheless, an update of this classification is desirable for it to be suitable for all thymic epithelial tumors including thymic carcinoma and carcinoid. The tumor-node metastasis (TNM) system classification and clinical staging system for thymic epithelial tumors have not been established yet. Until now, four TNM staging systems have been proposed: Yamakawa and Masaoka in 1991 (Y-M system), Tsuchiya et al. in National Cancer Center Hospital of Japan in 1994 (NCCHJ system), the World Health Organization Consensus Committee in 2004 (World Health Organization system), and Bedini et al. in National Cancer Institute of Italy in 2005 (NCII system).Methods:In this study, we show survival curves of thymic epithelial tumors (n = 1320) including thymoma, thymic carcinoma, and carcinoid according to the Y-M system.Results:The 5-year overall survival rates of stage I, II, III, IVA, and IVB thymic epithelial tumors were 94.2%, 91.2%, 70.5%, 56.3%, and 38.2%, respectively. Significant differences in survival rates were observed between stages II and III (p < 0.0001), stages III and IVA (p = 0.0205), and stages IVA and IVB (p = 0.0192).Discussion:This TNM staging system is an excellent predictor for the prognosis of thymic epithelial tumors including thymic carcinoma. The N and/or M factors influence the prognosis more than T factor. For the subclassification of the N and/or M factors, large-scale studies including the resectable and unresectable tumors are necessary.