Evaluation of the relationship between the eighth edition of TNM staging, the mMasoaka, and World Health Organization histopathological classification for thymoma

Abstract

Aim of study: The aim of this study was to describe the correlation between the eighth tumor, node, and metastasis (TNM), mMasaoka staging, and the World Health Organization (WHO) histopathologic classification and to identify prognostic values in predicting survival and recurrence of thymoma.

Materials and methods: Medical files of 90 patients with thymoma diagnosed between 1992 and 2018 were evaluated for this trial.

Results: The distributions of patients were similar between mMasaoka and eighth TNM staging according to early (I, II) and advanced stages (IIIA, IIIB, IV). Interestingly, 55 of 63 stage I patients with TNM staging showed difference as 31 of them up-staged to stage IIA and 24 of them up-staged to stage IIB in mMasoaka staging. Both staging systems closely correlated with WHO classification (p < 0.001); stages I and II were associated with low-risk groups (type A, AB, B1), and stages III and IV were associated with high-risk groups (type B2, B3). WHO classification was not a prognostic factor for overall survival (OS) ( P = 0.13) and progression-free survival (PFS) (p = 0.08), but it was a prognostic factor for 10-year cancer-specific survival (CSS) (p = 0.04). Myasthenia gravis was associated to early stages (stage I, II) (p = 0.007) and related with better prognosis.

Conclusions: Our study showed a correlation between both staging system and WHO classification. A certain difference was found between eighth TNM staging and the mMasoaka staging in terms of stage I disease. Both staging systems effectively prognosticated OS, CSS, and PFS. To clarify the prognostic relevance and clinical usefulness of the WHO classification may be beneficial in clinical practice for the treatment decision.