Necrosis is the process of cell or tissue death resulting from the activities of disease organisms, toxins or physical factors (e.g., temperature), as well as inadequate nutrition or starvation (e.g., as a result of an interrupted blood supply). Necrosis contrasts with apoptosis, which is the genetically programmed death of cells.

Pathologically, necrotic tissues undergo characteristic changes over time. On the macroscopic (visible) level, all necrotic tissues except for the brain undergo a definite colour change and acquire a firm consistency within the first 24 hours. In two to three days, a border delineated by an inflammatory response is observed, which may have fibrinous exudate. After one week, a gray/white periphery zone, due to healing via fibrosis, is seen and after several months, a fibrous scar has developed. In the brain and in infected tissues, macroscopic changes involve initially a softening and loss of tissue definition leading...