Simultaneous Resection for Type A Thymoma With Synchronous Solitary Pulmonary Metastasis: A Case Report

Type A thymoma is associated with an excellent prognosis, and distant metastasis is uncommon. Optimal management for metastatic type A thymoma has not been well documented. We report a case of conventional type A thymoma with synchronous solitary pulmonary metastasis treated with simultaneous resection. An 81-year-old woman was incidentally found to have both a 2.0 cm anterior mediastinal nodule and a 0.9 cm pulmonary nodule in the left lower lobe. Both lesions were resected via video-assisted thoracoscopic surgery. Histopathology and immunohistochemistry revealed identical features in both tumours, confirming type A thymoma with solitary pulmonary metastasis (pT1aN0M1b, stage IVb). No histopathological features of atypical type A thymoma were present. The patient remains recurrence-free 1 year after surgery without adjuvant therapy. This case suggests that pulmonary metastasis can occur even in small, low-grade type A thymoma and that simultaneous resection for diagnostic and therapeutic purposes may be considered to achieve favourable outcomes.