Relapse following adjuvant paraaortic radiation therapy in patients with Stage I seminoma is rare, occurring in approximately 4% of men. The majority of relapses are sited in the pelvis but relapse in the mediastinum is also recognised. As such, radiological imaging using chest radiographs remains commonplace in follow-up. However, there are reports of the association of testicular cancers with sarcoidosis and sarcoid-like processes in the mediastinum, emphasising the importance of making histological diagnosis prior to commencement of any treatment. We report on two men treated for testicular seminoma who on follow-up developed mediastinal lymphadenopathy, which was initially assumed to be metastatic seminoma. Both patients underwent mediastinascopy and biopsy prior to commencement of anti-cancer therapy. In both cases, the biopsies showed sarcoidosis, and unnecessary anti-cancer treatment was avoided.