Late relapse of testicular seminoma in the posterior mediastinum

Patients with testicular seminoma are usually cured if they survive disease-free for 5 years after therapy. Late relapse can also occur but is rare. In particular, relapse of testicular seminoma in the form of a large mediastinal mass is extremely rare. We present here a 37-year-old man with a late relapse of a large testicular seminoma in the posterior mediastinum, encasing the descending thoracic aorta, and compressing the left atrium and left main bronchus on computed tomography (CT) and positron emission tomography (PET).