Benign tumors are not cancer. They can usually be removed and, in most cases, they do not come back. Most importantly, cells from benign tumors do not spread to other parts of the body. Benign tumors are rarely a threat to life. Malignant tumors are cancer.
Cancer cells can invade and damage nearby tissues and organs.
Cancer cells can also break away from a malignant tumor and enter the bloodstream or the lymphatic system. The spread of cancer is called metastasis. Most cancers are named for the type of cell or the organ in which they begin. When cancer spreads, the new tumor has the same kind of abnormal cells and the same name as the primary tumor. For example, if lung cancer spreads to the liver, the cancer cells in the liver are lung cancer cells.