We report the case of a 62-year-old male with a history of primary testicular non-Hodgkin's lymphoma, treated with orchidectomy. After 14 months, the patient developed left leg swelling and pain, and was diagnosed and treated as having leg vein thrombosis. 18F-FDG-PET/CT showed a relapse of testicular lymphoma in the cutaneous muscle tissue of the left leg.