Stage III thymoma: relationship of local invasion to recurrence.

OBJECTIVES: We investigated the relationships of recurrence site with the involved organ and cell type in patients with Masaoka stage III thymomas. METHODS: Records of 84 patients who underwent a complete resection of stage III thymomas between 1957 and 2005 were reviewed and then divided according to involved organ. The number of patients with cell types determined according to World Health Organization criteria were 2, 5, 7, 37, and 7 for types A, AB, B1, B2, and B3, respectively, whereas type was not determined in 25 patients. RESULTS: Lung invasion occurred in 58 patients, followed by invasion of the pericardium in 47 and invasion of the great vessels in 23. Recurrence occurred in 23 patients, which included 12 with pleural dissemination and 8 with distant metastasis, mostly in the lung. Lung invasion was seen in 8 of the 12 patients with pleural recurrence, whereas vascular invasion was seen in 6 of the 8 patients with distant metastasis. Local recurrence was less common. Disease-free survival after 10 years for all subjects was 74.2%, whereas it was lower for those with vascular invasion (46.1%) compared with those without invasion (87.1%, P < .05). Of the 23 patients with recurrence, World Health Organization cell types B1, B2, and B3 were seen in 2, 11, and 3 cases, respectively, whereas type was not determined in 7 patients. CONCLUSIONS: The pleural cavity and lung are common sites of recurrence of Masaoka stage III thymomas. It is important to establish an inclusive therapeutic strategy that considers the relationships of involved organs and sites of recurrence in these patients.