Coloured magnetic resonance imaging (MRI) scan of a patient's pelvis showing a tumour (red) on the prostate, viewed from the side, with the spine to the right. Prostate cancer is when cells in the prostate (a gland below the bladder in men) replicate in an uncontrolled manner, forming a tumour. This patient has stage 4 prostate cancer, which means it has spread (metastasised) to other parts of the body, making treatment more difficult. Symptoms of prostate cancer often take time to appear and may initially manifest as difficulty urinating once the tumour is large enough to press against the tube through which urine travels (urethra). If cancer has spread, further symptoms may appear depending on where the cancer has reached, including lower back pain, testicular pain, tiredness and weight loss. Treatment varies with each case, but can involve a combination of chemotherapy, radiotherapy, or surgical removal of the tumour.