Types of Necrosis

Types of Necrosis

• Coagulative necrosis: most common form of necrosis, characterized by protein denaturation and coagulation in the cytoplasm, and typically occurs in solid organs like the heart, liver, and kidney.
• Liquefactive necrosis: characterized by cellular destruction by hydrolytic enzymes, and typically occurs in abscesses, brain, and pancreas.
• Caseous necrosis: a combination of coagulative and liquefactive necrosis, characterized by a soft, cheese-like appearance, and is characteristic of tuberculosis.
• Fat necrosis: caused by the action of lipase enzyme on adipose tissue, resulting in a white, chalky appearance, and typically occurs in pancreatitis.
• Fibrinoid necrosis: characterized by necrotic tissue resembling fibrin, with a pink, homogenous appearance, and typically occurs in the lumen of blood vessels with hypertension.
• Gangrenous necrosis: a gross term to describe dead tissue, and can be classified as either dry (microscopically coagulative necrosis) or wet (microscopically liquefactive necrosis).

Apoptosis

• Apoptosis: programmed cell death, also known as "normal death", regulated by genes, and involves RNA and protein synthesis.
• Physiological apoptosis: occurs in fatty changes in the liver, cholesterol, glycogen storage diseases, carbon deposition, and anthracosis.

Pigments

• Lipofuscin: an endogenous pigment, yellow-brown in color, indicating wear and tear effect, and typically seen in the heart and liver.
• Hemosidrin: a golden yellow-brown granular pigment, found in areas of hemorrhage, and can be seen by Prussian blue stain.

Calcifications

• Dystrophic calcification: precipitation of calcium in necrotic tissue, with normal serum calcium, and typically occurs in fat necrosis, psammoma bodies, and atherosclerotic plaque.
• Metastatic calcifications: precipitation of calcium in normal tissue, associated with hypercalcemia, and typically occurs in hyperparathyroidism, renal failure, excess vitamin D, and metastatic cancer.

Cell Injury

• Reversible cell injury: characterized by ATP depletion, increase in cell membrane permeability, and influx of calcium, leading to activation of lipases and proteases, mitochondrial dysfunction, and decrease in oxidative phosphorylation.
• Irreversible cell injury: characterized by more severe membrane damage, mitochondrial dysfunction, release of lysosomal digestive enzymes, and nuclear changes.

Cell Death

• Necrosis: "premature" or "untimely" death due to "causes", and can be classified into different morphological types.
• Cell death: can be classified into necrosis and apoptosis.