[TNM classification of thymic epithelial tumors]

The five-stage classification system of thymoma (I, II, III, IVa, IVb) is now adopted widely. As the cases with lymphogenous or hematogenous metastasis are included in IVb, it is suggested that IV b includes various groups with different prognostic factors. This facilitates establishment of TNM classification of thymic epithelial tumours (thymoma, thymic cancer and thymic carcinoid). T factors correspond with the stages, I: T1N0M0, II: T2N0M0, III: T3N0M0, and IV a : T4 N0M0. N and M factors are as follows: N1 : restricted to the anterior mediastinal nodes; N2 : intrathoracic nodes; N3 : supraclavicular nodes; and M1 : hematogenous metastasis and/or extrathoracic nodes excluding supraclavicular nodes. Such criteria were used to classify IVb into any T N(1,2,3) M0, and any T any NM1. N criteria could divide the cases into the groups with proper populations in IV b thymoma, thymic carcinoma, and thymic carcinoid, respectively. The possible relationships between survival and TNM were investigated in thymic carcinoma cases. T, N, and M have a relationship with survival, respectively. This TNM classification is not yet authorized, but it is used in many clinics in Japan to determine the selection of therapy and estimate the therapeutic effect.