Tumors can be benign or malignant . Benign tumors are not cancer. They often can be removed and, in most cases, they do not come back. Cells in benign tumors do not spread to other parts of the body. Most important, benign tumors are rarely a threat to life.
Malignant tumors are cancer.
Cells in malignant tumors are abnormal and divide without control or order. These cancer cells can invade and destroy the tissues around them. Also, cancer cells can break away from a malignant tumor and enter the bloodstream or the lymphatic system . The spread of cancer is called metastasis .