Thymoma patients with pleural dissemination: nationwide retrospective study of 136 cases in Japan.

BACKGROUND: Thymoma is a rare mediastinal tumor with relatively slow growth. However, advanced-stage cases with pleural dissemination are occasionally encountered. The outcome of surgical resection for thymomas with pleural dissemination has not been clearly determined. METHODS: We retrospectively investigated the clinical records of 2,835 patients with thymic epithelial tumors that were treated from 1991 to 2010 in 32 institutions that participated in the Japanese Association for Research on the Thymus. In this study, we analyzed the clinicopathologic factors and prognosis of thymoma patients with pleural dissemination who underwent surgical resection. RESULTS: The thymomas with pleural disseminations numbered 148 cases (5.2% in the 2,835 thymic epithelial tumors). Surgical resection was performed in 136 cases. Pathologic Masaoka stages were classified as IVA (n=118) and IVB (n=18). In Masaoka stage IVA disease, the small number of disseminated pleural nodules (10 or fewer) was related to the curative resection. The prognosis was also better in these cases than in those with greater than 10 disseminated pleural nodules (certified during the operation; p=0.0057). Patients who underwent macroscopic total resection of disseminated nodules had a better prognosis than those with residual tumors (p=0.037). In stage IVA cases with complete resection (n=42), the efficacy of adjuvant chemotherapy, radiotherapy, or both was not demonstrated. CONCLUSIONS: Macroscopic total resection of tumors appears to be a promising prognostic factor in Masaoka stage IVA thymomas. The number of disseminated pleural nodules correlated with resectability.