Light micrograph of a test for prostate cancer using Prostate Specific Antigen (PSA) antibody labeling. Dye is injected into the prostate gland, and binds to proteins altered by prostate cancer cells to form PSA. The prostate gland is a part of the male reproductive system. It is located under the bladder and secretes seminal fluid. Prostate cancer is a common cancer in men. Symptoms include increased need to urinate. Treatment includes surgery and radiotherapy. Magnification 250x @ 35MM.