A 57-year-old woman was referred to our hospital for multiple nodules in the bilateral lower lung fields of a chest X-ray image. Her medical history included surgery for ruptured type A thymoma 15 years previously, and follow-up had been completed with no recurrence for more than five years post-surgery. Computed tomography demonstrated several nodules of various sizes in multiple lobes (Fig. 1A and B), which exhibited little uptake of 18F-fluorodeoxyglucose on positron emission tomography-computed tomography (Fig. 1C). The tumors were suspected to be metastases, despite these examinations having revealed no primary tumor. Bronchoscopy found a tumor with smooth edges in right B10 (Fig. 1D), from which a biopsy was performed. Histopathology revealed that the tumor was composed of proliferating spindle cells and infiltrating T cells which were positive for terminal deoxynucleotidyl transferase (Fig. 1E and F). Thus, the tumors were diagnosed as a recurrence of thymoma. The patient underwent surgical resection of several lung metastases twice at another institution. A few metastatic tumors that were difficult to resect continue to be followed up.

Fig. 1.

(A and B) Computed tomography shows bilateral nodules. (C) Positron emission tomography-computed tomography shows the tumors have little uptake of 18F-fluorodeoxyglucose. (D) Bronchoscopic examination shows a tumor with smooth edges in right B10. (E and F) Histopathology reveals that the tumor is composed of proliferating spindle cells and infiltrating T cells which are positive for terminal deoxynucleotidyl transferase (TdT) (E: H/E staining, ×20, F: TdT staining, ×20).

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Thymoma recurrence after surgery occurs in less than half of the patient population, and most recurrences appear in the form of pleural dissemination.1,2 Surgery for pulmonary metastases of thymoma, which are relatively rare, can be an option.3 Complete resection of recurrent thymoma can result in a favorable outcome.4,5 In the present case, although rare, the tumors which were suspected to be hematogenous metastases could be observed and diagnosed by bronchoscopy examination as a recurrence of thymoma. Due to the long duration of recurrence, the patient underwent surgical resections twice, albeit incomplete resections.