Malignant refers to the presence of cancerous cells that have the ability to spread to other sites in the body (metastasize) or to invade nearby and destroy tissues. Malignant cells tend to have fast, uncontrolled growth and do not die normally due to changes in their genetic makeup. Malignant tumors are cancerous and are likely to spread beyond their point of origin. They can invade nearby tissues and spread to distant sites via the bloodstream or the lymphatic system, a process called metastasis. Malignant tumors can spread rapidly and require treatment to avoid spread. If they are caught early, treatment is likely to be surgery with possible chemotherapy or radiotherapy. If the cancer has spread, the treatment is likely to be systemic, such as chemotherapy.