Malignant disease refers to a type of disease, most commonly cancer, characterized by uncontrolled cell growth that has the potential to invade surrounding tissues and spread to distant parts of the body (metastasize). Key characteristics include: Uncontrolled Proliferation: Cells divide and grow without regard to normal regulatory mechanisms. Invasion: Malignant cells can infiltrate and destroy nearby healthy tissues. Metastasis: They can break away from the primary tumor, travel through the bloodstream or lymphatic system, and form new tumors in other organs. Malignant tumors are contrasted with benign tumors, which grow locally and do not spread to other parts of the body.