A 64-year-old man with history of prostate adenocarcinoma underwent radical prostatectomy in 2003. He remained with undetectable prostate-specific antigen (PSA) levels until 2014, when he then presented rising serum PSA levels and performed a Tc-MDP bone scan that was negative for metastases. In August 2015, his PSA was 4.89 ng/dL, and restaging images with pelvic MR and F-FDG PET/CT were both negative. Therefore, the patient underwent a Ga-PSMA PET/CT that showed marked tracer uptake in a single mediastinal lymph node. Histopathology demonstrated metastatic adenocarcinoma secondary to prostate cancer, altering patient management to hormone therapy instead of pelvic radiotherapy.