Prostate tumour. Coloured ultrasound scan of a section through the pelvis of a 52 year old man with an adenoma of the prostate gland (blue). Adenoma is a benign (non-cancerous) tumour that is most common in men over 50 years of age. It enlarges the prostate, causing it to press on the urethra, the tube urine passes through, causing problems with passing urine. Treatment is either with drugs to make the prostate shrink, or the surgical removal of the prostate.