Thymic cancer mimicking a metastasis of testicular seminoma

A 48-year-old man presented with a left testicular mass. Computed tomography showed an anterior mediastinal tumor, with positive uptake in positron emission tomography images. Radical orchiectomy was performed; the histology was seminoma. Thus, a diagnosis of testicular seminoma with thymic metastasis (stage III) was made and he underwent four courses of bleomycin, etoposide and cisplatin chemotherapy. The tumor shrank from 2.5 to 1.4 cm, but grew to 1.9 cm 1 month after the fourth course. He underwent two courses of paclitaxel, ifosfamide and cisplatin chemotherapy, followed by the resection of mediastinal tumor, the histopathological diagnosis of which was thymic cancer. Adjuvant radiation therapy was administered and no recurrences were evident at 1 year postoperatively. This is the first reported case of thymic cancer coexisting with stage I testicular seminoma.