A benign tumor is not a malignant tumor, which is cancer. It does not invade nearby tissue or spread to other parts of the body the way cancer can. In most cases, the outlook with benign tumors is very good. But benign tumors can be serious if they press on vital structures such as blood vessels or nerves. A malignant primary tumor is more dangerous because it can grow quickly. It may grow into or spread to other parts of the brain or to the spinal cord. Malignant tumors are also sometimes called brain cancer.