A 63-year-old male presented with complaints of an enlarging left supraclavicular mass and weight loss. Computed tomography demonstrated a large retroperitoneal mass causing displacement of the adjacent organs, and moderate left hydroureteronephrosis. Multiple pulmonary nodules, lytic spinal lesions, and generalized lymphadenopathy including the left supraclavicular region were seen. Serum prostate-specific antigen level was 2064.0 ng/mL. Digital rectal exam revealed an enlarged prostate without nodularity. Biopsy of the supraclavicular node demonstrated prostatic adenocarcinoma. The diagnosis of lymphoma may be initially suggested, however, prostatic origin should be considered even when the prostate exam is not grossly abnormal.