A tumor is an abnormal growth that may be benign or malignant. Benign breast tumors are not life-threatening and do not spread to other parts of the body. Malignant breast tumors are cancers that impact your health and may spread to other parts of the body. A malignant tumor that grows into surrounding tissue is considered invasive. Invasive tumors are more likely to spread to other parts of the body than non-invasive tumors. Non-invasive breast cancer cells remain in a particular area of the breast without spreading to surrounding tissue, lobules or ducts.