Histopathological analysis revealed a cribriform architecture, and immunohistochemical staining was positive for prostrate-specific antigen (PSA), NKX3.1, and alpha-methylacyl-CoA racemase (AMACR), leading to a diagnosis of metastatic prostate adenocarcinoma rather than a recurrence of RCC. Subsequent evaluation identified a primary prostate cancer (Gleason score 8, cT2cN0M1), and the patient achieved a favorable response with androgen deprivation therapy. The gene discussed is AMACR; the disease is prostate cancer.