Prostate cancer. Coloured scanning electron micrograph (SEM) of tissue from the prostate gland of a patient suffering from prostate cancer. The cells lining the acini (red/brown), the secretory units of the gland, are seen here. Malignant cells divide rapidly and chaotically, and can clump to form tumours which invade and destroy surrounding tissues. The prostate gland is a part of the male reproductive system located below the bladder. Prostate cancer can cause difficulty in passing urine and an increased need to urinate. Magnification unknown.