Secondary bone cancer in a fifty-seven year old male,oloured X-ray. This metastasis (secondary cancer) of the bone has arisen from a primary cancer of the prostate gland. Cancer cells travel from the prostate to the spine through a system of veins known as Batson's plexus. The cells cause compression of the spinal cord, as shown here at the second lumbar vertebra (orange). This compression causes pain and weakness of the legs and in extreme cases can lead to paralysis. The cancer cells also cause the bones around them to become thicker and more dense, as seen at the fourth and fifth vertebrae (bottom). Treatment is radiotherapy or hormone therapy.