What you need to know Signs and symptoms of skull base tumors depend on the type, location and size of the tumor. Most skull base tumors grow inside of the skull, but some form on the outside. Tumors may originate in the skull base or spread there from cancer elsewhere in the body (metastatic). Treating skull base tumors and conditions is challenging because they are close to critical nerves and blood vessels in the brain, head, neck, and spinal cord. Skull base tumors can sometimes be removed surgically. Techniques include minimally invasive endonasal endoscopic removal through the nose or through a small incision in the eyebrow or behind the ear. There is no obvious cause for skull base tumors. Radiation therapy to the head, specific genetic conditions and exposure to certain toxic chemicals may increase the risk.