death of a circumscribed area of plant or animal tissue as a result of an outside agent; natural death of tissue is called necrobiosis. Necrosis may follow a wide variety of injuries, both physical (cuts, burns, bruises) and biological (effects of disease-causing agents). The sign of necrosis—dead tissue—is called a lesion; (lesion) it is often of diagnostic value. Necrosis is brought about by intracellular enzymes that are activated upon injury and proceed to destroy damaged cells.