The Batson venous plexus (Batson veins) is a network of valveless veins in the human body that connect the deep pelvic veins and thoracic veins (draining the inferior end of the urinary bladder, breast and prostate) to the internal vertebral venous plexuses. Because of their location and lack of valves, they are believed to provide a route for the spread of cancer metastases. These metastases commonly arise from cancer of the pelvic organs such as the rectum and prostate and may spread to the vertebral column or brain. There is less evidence of spread of cancers from extra-pelvic origins, such as lung cancer. The plexus is named after anatomist Oscar Vivian Batson, who first described it in 1940. Batson's plexus is part of the Cerebrospinal venous system.