Background: Once an anterior mediastinal tumor has been diagnosed as a thymoma, complete excision including the thymic gland and perithymic fat is currently the procedure of choice. However, little is known about the clinical outcome of grossly encapsulated thymomas excised only with the surrounding tissue while leaving a part of the thymic gland.
Methods: A retrospective historical comparative study was conducted on 79 patients who had received surgery for stage I (n=25) or stage II (n=54) thymomas. Total thymectomy was performed in 61 patients (Total Thymectomy Group), whereas resection of tumors with only the surrounding tissue was carried out in 18 (Limited Thymectomy Group). The follow-up interval was longer in the Limited Thymectomy Group because these patients were treated longer ago (104.2+/-58.1 months vs 67.3+/-54.8 months, p<0.05).
Results: One case in the Limited Thymectomy Group showed postoperative myasthenia gravis (5.6%). Two patients with multiple thymomas (2.5%) were treated with total thymectomy. One case in the Limited Thymectomy Group, which had been diagnosed as Masaoka stage II and WHO type B3 at initial surgery, recurred. None died of tumor progression in this study. Disease free survival rates at 10 years did not differ between the Limited Thymectomy and Total Thymectomy Groups (85.7% and 82.0%, respectively). There were no statistical differences in the incidence of postoperative myasthenia gravis and disease free survival between the two groups.
Conclusion: Resection of thymomas with surrounding tissue instead of total thymectomy can be indicated for stage I or II thymomas in light of disease free and overall survival, post-operative onset of MG, and the incidence of multiple lesions.
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